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 Mr. Obama for a Republican  although contrary to claims by both supporters and opponents, his voting record places him, with Senator Clinton, more or less in the center of the Democratic Party, rather than in its progressive wing.