Rand Paul’s shirts always seem to fit. Look at almost any picture of him: The jacket lapel is always touching the tip of his collar, if only just barely. His untamed curls notwithstanding, he looks professional, put together, serious. The junior senator from Kentucky wasn’t wearing a jacket when I sat down with him in the Russell Senate Office Building a week before he mounted his 13-hour filibuster of John Brennan (whose confirmation as the next director of the CIA appeared, when this magazine went to press, more or less likely), but if he had been, you can bet that his lapel would have lined up perfectly with his spread collar.

Despite the looming sequester, foreign policy seemed to be on Paul’s mind. Three weeks earlier, in a speech at the Heritage Foundation, he had called himself a foreign policy “realist, not a neoconservative or an isolationist.” It’s a label he appears to have adopted recently; the word does not appear in either of his two books, The Tea Party Goes to Washington and Government Bullies, nor was it used to describe his foreign policy stance during the 2010 Kentucky Senate race. But he seems to be feeling his way toward a clear definition of realism, at least as he understands it.

“Neoconservatives seem to want boots on the ground everywhere, to be involved in every single war around the world,” Paul said in our interview. “Isolationists want us never to be involved anywhere around the world. Realism is a sort of in-between position.”

Practically, Paul’s brand of realism has two dimensions. First, don’t ever go to war without congressional authorization.

“You might repel an imminent attack,” he said, “but even if you repel an imminent attack today, you come to Congress within a day and say, ‘We’ve been attacked by Japan. They bombed Pearl Harbor.’ In those days, they came to Congress, asked for a declaration of war, and they got it.”

“And,” he quickly added, “I think we would have gotten one in Afghanistan as well.”

About the need for a formal declaration of war, as opposed to the resolutions and authorizations—Gulf of Tonkin, Desert Storm, Enduring Freedom, New Dawn—favored in the last half century or so, he is emphatic. (The last such declaration passed by Congress was against Bulgaria in 1942; the House and the Senate carried it without a single nay vote.)

The second component of Paul’s realism, in keeping with the thinking of realist luminaries like George F. Kennan (whom he mentioned in his Heritage address) and Henry Kissinger, is the national interest.

“A realist also asks, ‘Is there a vital national interest involved here? Is someone attacking our soldiers or our people?’ You have to look at the specifics, the pros and cons, and weigh actual evidence,” Paul said. “It’s not that we should never get involved. I would have us get involved only when our vital interests are affected.”

THIS APPROACH—sober, empirical, more than a shade utilitarian—seems to explain more than just Rand Paul’s foreign policy. When he was elected to the Senate in 2010, some hoped that he would take up the ideological torch of his father: libertarian, former congressman, and perennial presidential candidate Ron Paul. These expectations put him between the devil and the deep blue sea: on one hand, staunch Kentucky Republicans, and on the other, the coterie of libertarians and paleoconservatives who supported his father.

Take Chuck Hagel, President Obama’s nominee for secretary of defense. Paul supported the GOP’s filibuster of the nomination, but then ultimately voted for Hagel’s confirmation. In doing so, he seems to have pleased no one.

Before being ushered away to a conference room for our interview, I had plopped down on the couch in Russell 208 and thumbed through a copy of Reason while listening to a member of his staff take phone calls about Hagel. It’s an odd thing hearing only one end of a telephone conversation between a calm legislative functionary working from a mental script and a frazzled constituent: “He supported the filibuster…Senator Paul is a friend of Israel…I am speaking English, sir.” The tone, patient but direct, the sentences, simple and declarative, the unambiguous verbs carefully stressed: Her sapphiric clarity did not quite mask the audible strain and frustration. “A lot of these calls today?” I asked her. “Oh, yes,” she said.

For every incensed Kentuckian who holds his ultimately inconsequential vote against him (Hagel would have been confirmed by a nine-vote margin even if Paul and the other three Republicans who jumped ship had stayed on board), there is a paleoconservative or libertarian smarting from his support of the Hagel filibuster. Scott McConnell, one of the founders of the American Conservative, has gone so far as to suggest that Paul is in danger of becoming “Bill Kristol and Jennifer Rubin’s boy.”

Paul said he doesn’t see Hagel, who voted for the Patriot Act and the Iraq war, among other things, as a model libertarian. And he says he voted for Hagel in deference to the president—or at least that is what I gathered from the somewhat wayward five-minute response Paul gave when I asked him the question directly.

“It’s one of those things that a lot of people don’t think about when they’re not in the position of being in the U.S. Senate,” he said. “I don’t feel like I have an obligation to the president to vote yes on an issue where I disagree with him. On nominations it is a little bit different. If you win the election, you really should get to choose your cabinet. I ended up deciding that the president gets some latitude and leeway.”

Paul explained his support of the filibuster in coldly procedural terms. He insisted that going after Hagel was just a stepping stone. His real target was John Brennan, Obama’s choice for CIA director.

“I want information on him,” he said. “I figured we’re only getting information on Brennan if we stick together and try to get information on Hagel. Next we’ll go after Brennan. Well, the [Hagel] filibuster failed, and everybody gave in. Now we have no leverage.”

A week after our interview, Paul took matters into his own hands with an old-fashioned talking filibuster. He held the floor from just before noon to just after midnight, the ninth most prolonged act of obstruction in the history of the Senate. For hours, he stood alone, but the effort snowballed as other GOP senators joined in, and by the end even Majority Leader Mitch McConnell had taken a turn at the podium.

Whether Paul was seriously pessimistic about a Brennan filibuster or was keeping mum around the press when I spoke with him, I have no idea. Harold Wilson once said that a week is a long time in politics. It may have been an especially long week.

WHICH BRINGS us back to Rand’s father, the 12-term Texas congressman, and, oddly enough, back to shirts. Ron Paul’s shirts never fit. His lapel never reached his collar, not even in official campaign photos. (The suits themselves tended to be Reagan-era relics in bland presidential blue, most of them baggy and threadbare.)

The elder Paul was no master of political maneuver. Filibustering has not been an option in the House of Representatives for over a century and a half now, but even if it were still available, it is hard to imagine Ron Paul checking his hidebound constitutionalism long enough to support a talkathon for purely strategic reasons. It is even harder to imagine him securing the support of his colleagues, including the leadership of his party, for a hypothetical filibuster. If he thinks x is right and y is wrong, he won’t vote for x even if doing so gives him a bargaining chip when it comes to y. If being an effective—if not necessarily principled—member of Congress means being able to get legislation passed, then Ron Paul in his quarter-century-long political career was one of the least effective congressmen in American history. Only a handful of the hundreds of bills sponsored by Paul were ever debated on the House floor. Out of these, only two (including one of his innumerable “Audit the Fed” bills during his final year) passed the House. The single piece of Paul-authored legislation to have been signed into law, in January 2009, allowed the Galveston Historical Society to purchase a piece of federal property located in the coastal Texan city.

After only two years in the Senate, Rand Paul has already proven himself both less extreme and, perhaps unsurprisingly, at least marginally more successful as a legislator. Compare the records of father and son: Rand wasn’t the quixotic lone vote against giving a medal to Rosa Parks or condemning the Armenian genocide. Nor did he introduce legislation abolishing the income tax or allowing the private minting of gold and silver coins. Rand has written no pamphlets about restoring the gold standard or eliminating the Federal Reserve outright. On the subject of those evil acronyms (UN, NATO, NAFTA) at the mention of which the gorges of paleos everywhere rise in fury, he has been virtually silent.

He’s also much better—more photogenic and coherent, less shrill or outré—on television than his father. The elder Paul was always eloquent enough on paper, but on screen, say, during the 2008 presidential debates, his sentences were gnarled messes of abandoned clause and non-sequitur. In cases where his syntax was sure, his voice was reedy and his posture thoroughly awkward. Even when he was more or less on target, there was something about his appearance, his way of approaching his subject and framing his argument, that, for good or ill, just didn’t work in the television medium. Paul’s memorable exchange at a GOP debate about blowback (including, potentially, 9/11) from American foreign intervention calls to mind nothing so much as a tweeded, pipe-smoking professor trying to convince a group of haughty undergraduates of the importance of his latest hypothesis. Dubious or not, Paul’s blowback argument was never going to triumph rhetorically over Rudy Giuliani, who duly proceeded to exploit his 9/11 experience in response.

Even in 2012, when his criticism of the Federal Reserve began to find a place within the establishment conservative wing of his party, Ron Paul was never quite able to shake off the effluvium of nasty early-’90s newsletters that bore his name (“Duke lost the election, but he scared the blazes out of the Establishment”), ties to the John Birch Society, and repeated endorsements from conspiracy maven David Icke. The tang of fringe hangs around him even in retirement.

Rand, meanwhile, has been swimming comfortably in the mainstream for two years now. He doesn’t play these games, and he’s no one’s dancing bear or class nerd. When he appears, as he frequently does, on Fox News, he is relaxed, charming, and on-message. When asked about out-of-control federal spending, he doesn’t start complaining about Bretton-Woods or honoring the memories of 18th-century statesmen. Instead, like a Good Republican, he blames President Obama for his failure of leadership and castigates Democratic (or, as he would have it, “Democrat”) senators for their laziness and venality.

The Kentucky senator has certainly come a long way from the early blunders and snafus of his 2010 campaign. The race was roiled when GQ reported on college pranks in which Paul had allegedly participated, including a bizarre incident involving a secret society and prayers to “Aqua Buddha.”

More serious was his philosophical discussion (with Rachel Maddow) of the 1964 Civil Rights Act’s various shortcomings—whether, for instance, the government had the right to forcibly desegregate private restaurants. After criticism, he walked back his statements and said the constitutional issues had been settled by federal courts in the intervening years.

This is the balance he still strikes. “There’s always a question of when does the federal government go too far, what are the ramifications of saying what is a public, what is a private place?” he asked, before adding, “I would have voted for the Civil Rights Act whether I had misgivings or not.” In Paul’s case it’s possible to take this claim seriously: In 1964 both of Kentucky’s senators, Republicans John Sherman Cooper and Thurston Ballard Morton, voted aye.

Racial injustice, by the way, seems to be a subject very close to Paul’s heart. He spoke enthusiastically about George C. Wright’s Life Behind a Veil, an academic history of race relations in postbellum Louisville. He pointed out that in 1931 there were more than 25,000 registered black Republicans in the city, and only 129 Democrats.

“The Democrat-controlled legislature voted against the 13th, 14th, and 15th Amendments,” he said. “One hundred fifty years ago the editor of the Courier-Journal, now a liberal paper, said that he did not think that blacks would ever have the intellectual capacity to vote. I think this is the history people should try to remember. Republicans were the party of emancipation and voting rights.”

On education and immigration, both racially charged issues these days, Paul’s tone, if not always his actual thinking about policy, calls to mind the big-tent rhetoric of Jeb Bush. In a February op-ed in the Washington Times, Paul argued: “When every child can, like the president’s kids, go to the school of their choice, then will the dreams of our children come true.”

I asked him, after quoting a passage from Charles Murray’s essay “The Age of Educational Romanticism,” whether simply increasing opportunities was really the answer to America’s much-talked-about education crisis. Surely there are certain innate limits to what some of us can accomplish academically.

“I think Charles Murray is a really smart guy. I’ve read a couple of his books,” he responded. “But that’s a pessimistic way of looking at things.” He pointed to Jaime Escalante, the Bolivian calculus teacher lionized by the 1988 film Stand and Deliver. “Nobody had ever contemplated teaching these kids calculus. They were Hispanic kids, and everybody had given up on them, when in reality they had great potential.”

Paul was tapped to give a Tea Party response to this year’s State of the Union address, and his comments on immigration shocked some of his followers. He called for the GOP to become “the party that embraces the immigrant who wants to come to America for a better future…the party who sees immigrants as assets, not liabilities.” Previously he had come out in favor of ending birthright citizenship for children of illegal immigrants, even if it required amending the Constitution. During the 2010 campaign his website hosted detailed plans for an electronic border fence and a system of helicopter-monitoring stations.

So far, however, Paul has not endorsed John McCain–style amnesty legislation, which makes his apparent about-face seem less substantive than stylistic. Paul certainly seems to think that his party should do everything it can to improve its chances with minority voters.

“We need to convince those who live in primarily African American or Hispanic areas that the Democrat Party is not their friend,” he said, adding with, I think, more than a hint of sober practicality, “If we can transmit that message, it might be the transformative thing that changes the Republican Party from a shrinking white person’s party to an expanding party that has opportunities for Latinos and African Americans.”

THE LIST of things Paul is not is a long one. By his own admission he is not a neoconservative. He is also probably not, as many of his early supporters had hoped, a taller, better dressed, more charismatic version of his father. Nor is he a Lindsey Graham–style moderate or a John McCain–style “maverick.”

On balance, the label that fits best is probably that of conservative pragmatist. This tradition, with its roots in the approaches of Dwight Eisenhower and Richard Nixon, has, alas, fallen upon hard times. Most right-wingers under the age of 40 are as likely as not to have made up their minds about the 37th president after reading Hunter S. Thompson. The majority of Tea Party members are, with the best of intentions, out for blood, and Paul’s talent for sniffing out the right pieces of red meat to toss their way has made him the closest thing the movement has to a leader in the U.S. Senate. But he may yet prove to be a sheep in wolf’s clothing, a Tricky Dick wearing a tri-cornered hat who does his best to identify the concerns of the Republican base and carry them to their practical, if not necessarily logical, conclusions.

When my time with Paul was up, I asked whether we could squeeze in one more question. Rocking lightly in his chair, he laughed, saying, “You saved the hardest one for last.”

Paul says he has no idea whether or not he will seek the presidency in 2016. He might even be telling the truth. There is no way of knowing how he might fare either in a series of what are sure to be densely packed GOP primaries or in a general election against an unknown Democratic challenger. What is clear, though, is that if Rand Paul does run, he will be, in the cant phrase, in it to win it.