President Obama's re-election on Tuesday had its roots in his historic landslide victory four years earlier: Though he ceded plenty of the ground he won then, his message and his vaunted grassroots operation were enough to win over his staunchest supporters, who turned out in force to ensure him a second term.

"He was able to bring a lot of people to the table again," said Mike Gousha, a Marquette University political analyst. "With some of the constituencies that helped him get elected in 2008, he did very well again. While the margin wasn't like it was four years ago, it was enough."

Pending the outcome of Florida's vote, Obama could capture up to 332 electoral votes, still 33 fewer than he got in 2008. Overall, he's seen his support drop in 41 states and the District over the past four years, and he emerged the winner Tuesday by one of the narrowest margins in the popular vote.

Still, Obama's victory was more comfortable than late polls suggested it would be, and the scramble for electoral votes wasn't all that close even though Obama's support among one key bloc of voters -- white men -- dropped even further.

Romney did better than 2008 Republican nominee John McCain among men, women, whites and blacks. But Obama offset that increased support for his opponent by building an enormous advantage among blacks and women. He also bumped up his margins among Hispanics by 4 percent since 2008 and by 11 percent among Asian-Americans.

"Democrats pounded the Republicans using the demographics," said Craig Marks, a Virginia Tech political scientist. "The Republican Party has some things to consider."

The president succeeded also because he was able to blunt the main argument Romney made against him: that the president was to blame for the lingering recession. But enough voters faulted the president for the tough economic times that his margins of victory in key states like Colorado fell. He won the Centennial State by 4 percentage points on Tuesday, unofficial returns show. That's down from his 9-point margin in 2008.

"On the top issue, the president not only kept blame on [George W.] Bush but fought Romney almost to a draw," said Nathan Gonzales, deputy editor of the nonpartisan Rothenberg Political Report. "And if Romney didn't have the upper hand on the economy, he didn't have much left."

Obama's margins were also reduced in some states because Romney successfully cut into the president's support among women, primarily by talking about the impact the sagging economy is having on families. In Colorado, Romney was running nearly even with Obama among women, a far cry from the 14-point edge Obama had with those voters in 2008.

Michael Berry, a University of Colorado Denver political scientist, said the gender-based trends were a surprising variance from national views.

"There's got to be a good reason for it; I just don't know what that would be," Berry said of Obama's precipitous drop among Colorado women. "There's nothing that really I could point to in Colorado that was all that different."