After their victory in the 2006 congressional elections, it seemed a given that Democrats would try to make this year's presidential campaign another referendum on Republican policies.

After all, the public appears fed up not just with President Bush, but with his party. For example, a recent poll by the Pew Research Center shows Democrats are preferred on every issue except terrorism. They even have a 10-point advantage on "morality."

Add to this the fact that perceptions about the economy are worsening week by week, and one might have expected the central theme of the Democratic campaign to be "throw the bums out."

But a funny thing happened on the way to the 2008 election.

Unless Hillary Clinton wins big on Tuesday, Barack Obama will be the Democratic nominee. And he's not at all the kind of candidate one might have expected to emerge out of the backlash against Republican governance.

Now, nobody would mistake Obama for a Republican — although contrary to claims by both supporters and opponents, his voting record places him, with Clinton, more or less in the center of the Democratic Party, rather than in its progressive wing.

But Obama, instead of emphasizing the harm done by the other party's rule, likes to blame both sides for our sorry political state. And in his speeches he promises not a rejection of Republicanism but an era of postpartisan unity.

That — along with his adoption of conservative talking points on the crucial issue of health care — is why Obama's rise has caused such division among progressive activists, the very people one might have expected to be unified and energized by the prospect of finally ending the long era of Republican political dominance.

Some progressives are appalled by the direction their party seems to have taken: they wanted another FDR, yet feel that they're getting an oratorically upgraded version of Michael Bloomberg instead.

Others, however, insist that Obama's message of hope and his personal charisma will yield an overwhelming electoral victory, and that he will implement a dramatically progressive agenda.

The trouble is that faith in Obama's transformational ability rests on surprisingly little evidence.

Obama's ability to attract wildly enthusiastic crowds to rallies is a good omen for the general election; so is his ability to raise large sums. But neither necessarily points to a landslide victory.

Polling numbers aren't much help: for now, at least, you can find polls telling you anything you want to hear, from the CBS News/New York Times poll giving Obama a 12-point national advantage over John McCain to the Mason-Dixon poll showing McCain winning Florida by 10 points.

What we do know is that Obama has never faced a serious Republican opponent — and that he has not yet faced the hostile media treatment doled out to every Democratic presidential candidate since 1988.

Yes, I know that both the Obama campaign and many reporters deny that he has received more favorable treatment than Hillary Clinton. But they're kidding, right? Dana Milbank, the Washington Post national political reporter, told the truth back in December: "The press will savage her no matter what they really have the knives out for her, there's no question about it {hellip} Obama gets significantly better coverage."

If Obama secures the nomination, the honeymoon will be over as he faces an opponent whom much of the press loves as much as it hates Clinton. If Clinton can do nothing right, McCain can do nothing wrong — even when he panders outrageously, he's forgiven because he looks uncomfortable doing it. Honest.

Bob Somerby of the media-criticism site dailyhowler.com predicts that Obama will be "Dukakised": "treated as an alien, unsettling presence." That sounds all too plausible.

If Obama does make it to the White House, will he actually deliver the transformational politics he promises? Like the faith that he can win an overwhelming electoral victory, the faith that he can overcome bitter conservative opposition to progressive legislation rests on very little evidence — one productive year in the Illinois state Senate, after the Democrats swept the state, and not much else.

And some Illinois legislators apparently feel that even there Obama got a bit more glory than he deserved. "No one wants to carry the ball 99 yards all the way to the one-yard line, and then give it to the halfback who gets all the credit," one state senator complained to a local journalist.

All in all, the Democrats are in a place few expected a year ago. The 2008 campaign, it seems, will be waged on the basis of personality, not political philosophy. If the magic works, all will be forgiven. But if it doesn't, the recriminations could tear the party apart.

c.2008 New York Times News Service