by DHinMI

Who's favored in an election, the long-time leader or the fast-closing challenger? If the long-time leader is an incumbent, usually you figure the challenger has a solid chance to win. How might this pattern play out in the Democratic primary?

Hillary Clinton has been ahead in the national polls since the start of the campaign. But all the momentum, both long term and in the last few weeks appears to be with Barack Obama. In mid-October, the Pollster.com average of national polls had Clinton and Obama separated by 23 points, 46-23. Today the difference is down to 43/36, and Obama's ascent has been significant.

Look at the two tracking polls listed in Devilstower's polling roundup. A tracking poll is a rolling three day sample. You try to get approximately 400 respondents per night. Each day you add in the previous night's results and drop out the oldest results. Rasmussen's numbers have bounced around a bit in the last 10 days, but their latest 3 day average has the gap between Clinton and Obama at 7 points, and that's with only one night's sample without Edwards in the race. While one should not put too much stock in one night's data in a rolling three-day tracking poll, last night Rasmussen's single-night sample had Obama and Clinton "essentially even." And a look at the Gallup numbers from 6 days ago, 3 days ago and today show Clinton's margin over Obama shrinking from 16 point to 11 points to 4 points.

In elections with an incumbent, it's generally thought that if the challenger is close and gaining on the incumbent in to the final days of a campaign, then the challenger has the momentum and is the odd-on favorite to win. Technically there is no incumbent and no challenger in this race. But vice-presidents are often thought of as de facto incumbents in a Presidential primary.

While she's not a vice-president, in some ways Hillary Clinton is like a sitting vice-president running for the nomination. The comparison doesn't work perfectly here, as elections with a sitting vice-president are viewed in part as a referendum on the performance of the sitting president, and Bill Clinton has been out of office for 8 years, and the sour mood of the country isn't blamed on Bill Clinton. (Well, at least outside the pages of the American Spectator and in the bloviations of Rush Limbaugh.) But as the known commodity running against the fresh face, the alternative to what's already known--and for most casual political observers, Barack Obama is just now becoming familiar to them--Hillary Clinton is similar to an incumbent or a vice-president running for presidential nomination.

So, if we accept the flawed but still probably useful model of Hillary Clinton as the incumbent, Obama's momentum probably indicates that Tuesday's primaries and caucuses should be much closer than one would expect based on the prevailing conventional wisdom throughout most of this nominating campaign.

Hillary Clinton is still polling ahead of Barack Obama in most states. But with Obama's momentum and the narrow margins in the polls nationally and in several key states like California, it's not unreasonable to think that Barack Obama could come out ahead on Tuesday night.

Post courtesy of DHinMI from DailyKOS.