Even though Democrats have a doomsday mentality ("how are we gonna lose this time?"), many are now daring to believe that Barack Obama might actually win Tuesday. And the giddiest Democrats are even entertaining the notion that a solid Obama victory, coupled with enhanced Senate and House majorities, will usher in an extended era of Democratic dominance.

But I wouldn't bet good money on that.

Granted, a decent argument can be made that we're on the brink of a transformative election - a rarity in our political history, akin to 1860 or 1932 or 1968. The anticipated flood of new voters could help reshape the electorate; young voters, in particular, came of age during Iraq, Katrina and Bush, and those formative experiences could bond them to the Democrats for the long haul.

Moreover, voters seem more willing to see themselves as Democrats. In the latest nonpartisan Pew Research Center poll, 39 percent identified with the party (the highest Democratic share in 21 years of Pew polling), while only 24 percent identified with the Republicans (the lowest GOP share in those 21 years). The party-allegiance gap began to widen in 2006 - the same year that voters ejected the congressional Republicans from power - and it is notably strong in Pennsylvania, where the current registration gap, favoring the Democrats, is eight times wider than it was in 2004.

Those who foresee a Democratic realignment also contend that the nation is moving slightly leftward. The polls report that only a small minority of Americans support retention of all the Bush tax cuts. There seems to be little appetite for Social Security privatization; even when President Bush was at the peak of his popularity, he couldn't sell it. And most Americans have long judged the war in Iraq to be a disastrous mistake.

Meanwhile, the new Pew poll reports that 57 percent of Americans support government guarantees of health insurance for all, "even if it means raising taxes." Indeed, by a 1-point margin, Americans now favor "bigger government, more services" over "smaller government, fewer services" - in stark contrast to January 2001, at the dawn of the Bush era, when Americans favored the "smaller government" option by a 15-point margin.

The Democratic-dominance argument ultimately hinges on Obama's scoring a solid, broad-based victory in the nationwide popular vote. Historically, the bar for Democrats is not very high; if he merely surpasses 50.1 percent, he would be the first nonincumbent Democrat to do so since Franklin D. Roosevelt in 1932. And, geographically, he needs to break new ground by expanding the Democratic map - which he appears well-positioned to do, given his current prospects for winning traditional red states such as Colorado, Virginia, Nevada and North Carolina.

And yet, I still don't buy the Democratic-dominance scenario.

Stan Greenberg, a prominent Democratic pollster, suggested the other day that voters are interested in Obama "because of his steadiness," and not because of his progressive agenda. That sounds about right.

Swing voters - the folks in the middle of the electorate - checked out Obama during the three presidential debates, and judged him to be of keen intellect and good temperament, at a crisis moment when both traits are required. In terms of intellect, Obama is widely viewed as the antithesis of Bush; in terms of temperament, he is widely viewed as the antithesis of John McCain.

But just because Americans want something different, that doesn't mean that the nation is trending leftward; indeed, as top Obama strategist David Axelrod remarked in Newsweek the other day, "I think right now people are in a pragmatic mood, not an ideological mood." In other words, Obama is well-positioned to win not because of his liberal profile, but in spite of it.

Democrats have won only three of the last 10 presidential elections, and the winners (Jimmy Carter, Bill Clinton) were moderate Southerners who often warred with the liberals in their own party. Clinton won reelection in 1996 because he moved to the center and stole a number of Republican issues, notably welfare reform.

And Obama - mindful that contemporary America is actually slightly right of center - has been talking up tax cuts, invoking God and traditional values, and voicing his determination to kill terrorists. Meanwhile, he sidesteps the traditional liberal issues. He tries not to utter the phrases gun control or gay marriage. He defends abortion rights when asked to do so, but stresses his desire to reduce the number of abortions. He defends capital punishment. And he steers clear of the liberal camp's concerns about post-9/11 government surveillance.

Obama's caution suggests that he is attuned to the dangers of overreaching, that he and Axelrod are keen not to mistake a solid win for a sweeping ideological agenda. Victory would present Obama with an opportunity, not a mandate. Swing voters would be entrusting him to govern competently, using good ideas from both sides of the aisle. No longer would he be judged favorably in contrast to McCain or Bush; that's the easy part. Within a year or two, Obama (and the Democratic Congress) would be judged solely on the size of the gap between promise and performance.

And there would be little margin for error. It was a mere four years ago when Bush's top political guru was suggesting that an extended era of GOP dominance was at hand; in his words, "we may be seeing part of a rolling realignment." Well, the nation's pragmatic voters have apparently nixed his dream. And it would appear that the Obama camp has no desire to go the way of Karl Rove.