Original theory: Dude, we got this.

Follow-up theory: Dude, we’re DOA.

New and improved theory: Dude, it’s down to the wire.

As the general election campaign gets underway, Obama’s slim 49% to 45% edge over Mitt Romney is based on his continued support among women, college graduates, blacks, Latinos and lower-income voters. Obama leads Romney by 13 points among women, which is identical to his victory margin over McCain among women four years ago, according to National Election Pool exit polls. Men, who split their vote between Obama (49%) and McCain (48%), are leaning slightly toward Romney today, by a 50% to 44% margin…

Obama has lost support among several groups: Obama carried the independent vote by a margin of 52% to 44% in 2008. Today, 42% of independents favor him, while 48% back Romney. Obama also is faring worse among lower-income voters and those with less education than he did in 2008.

Obama trails Romney by a wide margin among white voters (54% Romney, 39% Obama), though that is little changed from 2008. But Obama has lost ground among certain groups of white voters. In 2008, whites with household incomes under $50,000 favored McCain over Obama by a slim 51% to 47% margin. Today, lower-income whites favor Romney over Obama by a 16-point margin (54% to 38%).

Follow the link for a useful side-by-side comparison of O’s numbers against McCain across various demographics and his current numbers against Romney. (Here’s the data about the sample. It’s based on 3,008 adults but only 2,841 identify as Democrat, Republican, or independent — and only 2,373 are registered voters. Among self-identified respondents, the split is 32.7D/27.7R/39.6I.) Dave Weigel’s right: In key groups that Dems are worried about, most notably independents and seniors, right now Obama’s off his 2008 pace and is doing just barely well enough to lead. In fact, Ron Brownstein took a hard look at all four major polls released over the last few days and spotted a pattern:

Even with their modest variations, these four surveys paint a similar picture. Obama is largely holding the minority and college-educated white women who comprise two pillars of the modern Democratic base (along with young people.) But he is facing erosion among blue-collar white men and struggling to maintain even his modest 2008 support among the two swing quadrants in the white electorate: the college-plus white men and non-college white women.

For the moment, that division of allegiances is enough to provide Obama an overall advantage (he would lead slightly even in the Gallup track if the minority share of the vote was adjusted to its level in 2008). But it’s not enough of an edge for him to breathe easy-and the fact that most of the white electorate is resisting him at least as much as it did in 2008 suggests he may never entirely get to such a comfortable place before November, even if he remains ahead overall.

No margin for error for The One this time. Meanwhile, CNN has new numbers via their screwy data set from yesterday, for what it’s worth: Romney’s favorable rating is up 10 points since February to 44 percent and his unfavorables are down 11 points to 43 percent. He still trails O in favorability and likely always will, but narrowing the spread at least reduces the chance that the “likability gap” will move votes among undecideds at the last minute. Then again, Romney may be benefiting here from a honeymoon period with the public now that he’s all but clinched the nomination. We’ll see what happens to these numbers once he and O start throwing roundhouses.

I’ll leave you with two noteworthy bits from the Pew poll. First, the shame of Republican negligence on spending:

Lots of factors help explain those 2004 numbers. One: The deficit was in fact much smaller pre-recession. Two: The war on terror was a top Republican priority at the time, and hawkish voters typically are willing to run deficits to justify a war effort. Three: There’s an obvious partisan effect here. Republicans clearly cut Dubya some slack early on (although a sizable majority were worried about deficits again by the time of Bush’s final year) and Democrats actually got more comfortable with the deficit after Obama took office despite the explosion of red ink. Even so, you’ve got a clear majority of Dems and indies worried about deficits across an eight-year span here but not until sometime between 2004 and 2008 do Republicans catch up. Note to GOPers: When you’re asked whether balancing the books is “very important” to your vote, the answer is yes.

Then there’s this:

Note the last four lines in particular. I flagged another poll showing something similar a few months ago but can’t find it in the archives right now. Plain and simple: For all the hype about conservatives and tea partiers feeling disgruntled about Romney, there’s no reason to think they’re staying home because of it. On the contrary, it’s the centrists who seem to be wavering on Mitt. That’s perfectly logical — centrists will consider voting for Obama whereas right-wingers won’t — but the myth of the spiteful anti-Romney grassroots conservative will feature in many an election story to come this year. Bear these numbers in mind whenever you come across it.