Over the past few weeks, conservatives contemplated John McCain’s vice presidential choice with a growing sense of foreboding. The names that were being floated included pro-choice Rudy Giuliani, all-around moderate Tom Ridge, and independent Democrat Joe Lieberman. Even Mitt Romney had his detractors and Tim Pawlenty could at best do no harm.

Goodbye to all that. Alaska Gov. Sarah Palin has rallied the conservative base like McCain himself never could.

Rush Limbaugh was ecstatic, crying, “Babies, guns, Jesus. Hot damn!” A caller paraphrased Michelle Obama: “For the first time in years, I am proud to be a Republican.” James Dobson called her an “outstanding” running mate who would secure his vote this fall. Notoriously hard-to-please conservative activist Richard Viguerie pronounced Palin “perfect.”

Pat Buchanan offered a more sober assessment of the onetime Buchananite’s value to the Republican ticket: “This is the biggest political gamble I have ever seen. She is enormously exciting but if, God forbid, something happens, can she be president?”

“Gamble” is exactly the right word. Palin is high-risk but also potentially high-reward. As a relatively young (44) first-term governor of a small state, Palin undercuts the experience argument against Barack Obama as much as Joe Biden undermines Obama’s message of foreign-policy prescience and change. If the pick is seen as unserious or as tokenism, if she stumbles once in the national spotlight, or if she falls victim to her own version of trooper gate, it could be one mistake too many for a Republican ticket that has little margin for error.

But the 2006 elections left the Republican bench in tatters and McCain, facing a Democratic opponent who would make history if elected, may not have had the luxury of a safe choice. If Palin succeeds, she can bring in women voters, including disgruntled Hillary supporters, without alienating pro-life social conservatives. She has already excited anti-McCain conservatives going into the Republican National Convention in St. Paul.

Republicans cannot be silent when Democrats claim there isn’t a dime’s worth of difference between Palin and Obama when it comes to their resumes. That doesn’t mean they should inflate her qualifications, by talking about her “foreign policy” dealings with Canada or status as head of Alaska’s National Guard. Instead the argument must be that where Obama talks about reform, Palin delivers.

When a sitting Republican governor proposed an unpopular petroleum profits tax at a rate favored by a company that illegally funded money to his reelection campaign, Palin took him on. When he bought himself a plane at taxpayer expense over the legislature’s objections, she committed to sell it if elected. Palin beat that governor by 32 points in the GOP primary.

Palin kept her promise to sell her predecessor’s plane. She locked swords with Sen. Ted Stevens over the Bridge to Nowhere, which she dismantled. She endorsed her Lt. Gov. Sean Parnell in a tight Republican primary against Congressman Don Young.

For all Obama’s talk about taking unpopular reformist stands, he has generally favored bipartisan ethics bills that pass by lopsided margins. He has seldom picked a fight with powerful members of his own party — unless they were running against him for public office — or any interest group in the Democratic coalition. And he lacks her track record of truly seeking to eliminate wasteful spending, a new commitment he adopted in his Denver acceptance speech.

To this writer, the biggest concern about Sarah Palin is not that she will hurt McCain but the opposite. A defeat would cause Palin to lose some of her luster. A McCain-Palin victory will deprive Alaska of an effective reformist governor and the conservative movement of a much-needed governing success story at the state level.

This is not to say the Palin pick can’t backfire. Neutralize the experience advantage and it makes it easier for the Democrats to turn this election into a referendum on George W. Bush. Republicans will not like the result of such a referendum. In politics, there are also always good reasons to fear the unknown. Palin may yet prove a political disaster.

But Palin has already bridged gaps within the GOP coalition that once seemed unbridgeable and deflected media attention away from Obama less than a day after the Invesco speech. There isn’t much upside in losing the presidential race narrowly. McCain is taking a big gamble, but in this case it is worth rolling the dice.