The Clintons have changed their tune. In 1992, Bill was a New Democrat who campaigned to the soft-rock sounds of “Don’t Stop (Thinking About Tomorrow).” Fifteen years later, Hillary is crooning “Yesterday.”

After all, the senator from New York hasn’t been shy about exploiting Clinton nostalgia in her stump speeches. Campaigning in Iowa last weekend, she took the old “two for the price of one” line to a new level by promising to make her husband a roving ambassador to the world. “I believe in using former presidents,” the Associated Press quoted her telling one crowd in Marshalltown.

Mrs. Clinton said that someone needs to stitch back together our country’s tattered world image after George W. Bush’s presidency. “I can’t think of a better cheerleader for America, can you?” she enthused.

But have no fear. While Bill is globetrotting, Hillary won’t just stay home having teas and baking cookies. She plans to revive much of the Clinton domestic-policy agenda and sell it with the same talking points her party used to great effect during the 1990s, from the federal budget to healthcare.

Take taxes, for example. Hillary says the wealthy once again “aren’t paying their fair share.” She promises to rectify that problem by raising their taxes at least back to the marginal rates they paid under her husband’s administration. When Senator Clinton complains about the deficit, runaway federal spending is low on her list of culprits but the soon-to-expire Bush tax cuts figure prominently.

And so does class warfare. “Rich people didn’t make this country great,” Hillary opined. “It was the middle class who made this country great.” It’s the classic Clinton mixture of populism and pretensions of economic centrism.

“We need to get back to fiscal responsibility,” she says, hearkening back to the budget surpluses the nation enjoyed the last time her family lived at the White House. Senator Clinton doesn’t believe the reformist congressional Republicans — the GOP has changed its tune since the ’90s too — were at all responsible for those surpluses, but she is convinced that her husband’s 1993 tax increase was. Perhaps in a very indirect way, she is right: That tax hike was an important reason there was a Republican Congress in the first place, alongside Hillary’s own health plan.

Senator Clinton plans to bring back that artifact from the previous administration as well. She doesn’t seem particularly embarrassed by her role in that political debacle. Indeed, her website plays it up. “As everyone knows, Hillary’s fight for universal health coverage did not succeed,” the Clinton camp allows delicately. “But her commitment to health care for every American has never wavered.”

It wouldn’t be Clintonian politics, however, without a little triangulation. So Hillary has made a few feints to the right on the cutting-edge issue of immigration — but not too far to the right. She advocates stronger employer sanctions on companies that hire illegal aliens, the get-tough approach most compatible with the liberal view of business. And she promises federal help to communities that bear heavy fiscal burdens due to unchecked illegal immigration.

Yet even here she borrows from Bill. The Clinton administration’s immigration enforcement record was in some respects tougher than Bush’s during his first term (the Clintonites carried out more worksite arrests of illegal aliens and imposed fines on more employers). For a while, it looked like the 42nd president might support the moderately restrictionist recommendations of Barbara Jordan’s mid-1990s immigration commission, though instead he ended up signing a tough-sounding bill that pleased neither side of the debate.

These seemingly disparate elements do add up to a coherent message: Let’s forget the ugly interlude of Bush’s two terms and return to the good old days when the Clintons were in power. Back to budget surpluses and high-tech booms, back to when people living in foreign countries loved American leaders. Back to a politics that is reliably liberal when it comes to protecting abortion and soaking the rich but not too soft on crime and sufficiently solicitous of middle-class interests.

With Bush’s approval ratings stuck below 40 percent and Iraq fatigue setting in among Democrats and independents alike, it ought to be an appealing message. What voter likely to choose a Democratic primary ballot next year wouldn’t prefer the policies of Bill Clinton to those of George Bush?

Hillary may nevertheless be misreading her party’s mood. Now that they no longer have to defend him against Newt Gingrich or Ken Starr, many liberals have come to view Bill Clinton as something of a sellout. The entire New Democrat project was an attempt to adapt to liberal weakness; the party’s activists want to take advantage of what they perceive to be a renewed liberal strength. The base isn’t looking for Sister Souljah moments this time around.

Nowhere is this dilemma more apparent than in Hillary’s tortured calculations on Iraq, the number-one issue for angry Democrats. Senator Clinton still won’t apologize for her pro-war vote because her kind of Democrat wants to maintain at least the appearance of national-security toughness when courting swing voters, but her party’s center of gravity is moving away from her.

Enter Barack Obama. It still remains to be seen if the freshman Illinois senator has what it takes to weather a serious national campaign. But Obama is someone who could rival Bill Clinton’s status as the Democratic Party’s biggest star. And he can through his personality project a contrived image of moderation that Hillary can only attempt through her proposed policy prescriptions.

In politics, nostalgia can only get you so far. Or as the sage members of Fleetwood Mac might put it: Yesterday’s gone, yesterday’s gone.