I live in Illinois and worked as a volunteer quite a bit on Barack Obama's 2004 Senate primary. The presidential campaign feels a lot like the Senate primary to me with late and ultimately overwhelming support for Obama.
Barack Obama was not supposed to win the Senate primary. He was clearly the most intelligent, articulate and progressive candidate in a crowded field of very good contenders, but because he didn't have the entrenched forces of the party behind him, he was considered to be a likely casualty of 'the way it is.' For most of the race, he was in third place.
Then about a month before the election (notice the similarity) he picked up steam in the polls and more importantly, in the public mood. Sentiment shifted. And in the last two weeks, a narrow victory turned into an avalanche of support with an incredible 53% victory in a seven-candidate field.
Today, a month before the first elections, the entrenched candidate who has all the institutional support in the world, is just starting to look beatable, largely because more and more people are getting behind Barack.
I think that's because the base of the Democratic Party (non-operatives like me who vote in primaries but don't donate much money and don't pay much attention to candidates until a few weeks before the election) have much more of a positive reaction and attachment to Barack Obama than conventional wisdom suggests or calculates.
And as Rich Miller of the Capitol Fax Blog has written extensively, black voters break late. For whatever reason, they attach to candidates late in the process (around now). That's part of the momentum for Obama.
I also saw it with white voters. I coordinated the 43rd Ward in Chicago for the Obama Senate primary and I did not ever anticipate an overwhelming victory. You can read about my reaction on my blog here. (Scroll down to the middle of the page -- the primary was March 17, 2004).
It feels very similar to me.
I'm predicting an Obama victory.