Doug Mills/The New York Times
President Obama greeted a volunteer during a visit to a local campaign office in Chicago.
Barack Hussein Obama was re-elected president of the United States on Tuesday, overcoming powerful economic headwinds, a lock-step resistance to his agenda by Republicans in Congress and an unprecedented torrent of advertising as the nation voted to give him a second chance to change Washington.
In defeating Mitt Romney, the president carried Wisconsin, Iowa, New Hampshire, Colorado and Virginia and was holding on to a narrow advantage in Ohio and Florida. The path to victory for Mr. Romney narrowed as the night wore along, with Mr. Obama steadily climbing toward the 270 electoral votes needed to win a second term.
A cheer of jubilation sounded at the Obama campaign headquarters in Chicago when the television networks began projecting him as the winner at 11:20 p.m., even as the ballots were still being counted in many states where voters had waited in line well into the night. The victory was far narrower than his historic election four years ago, but it was no less dramatic.
As a succession of states fell away from Mr. Romney, a hush fell over his Boston headquarters on Tuesday night. Two advisers said in interviews that the contest seemed over, but Mr. Romney was not conceding, with the electoral votes from Ohio and Florida still outstanding.
The evening was not without the drama that has come to mark so many recent elections: Even after Fox News Channel projected that Mr. Obama would win Ohio — effectively sealing Mr. Obama’s re-election — its on-air analyst, the Republican strategist Karl Rove, was arguing that it had done so too quickly and that Mr. Romney still had a chance.
Hispanics made up an important part of Mr. Obama’s winning coalition, preliminary exit poll data showed. And before the night was through, there were already recriminations from Republican moderates who said Mr. Romney had gone too far during the primaries in his statements against those here illegally, including his promise that his get-tough policies would cause some to “self deport.”
Mr. Obama, 51, faces governing in a deeply divided country and a partisan-rich capital, where Republicans retained their majority in the House of Representatives and Democrats kept their control of the Senate. His re-election offers him a second chance that will quickly be tested, given the rapidly-escalating fiscal showdown.
For Mr. Obama, the result brings a ratification of his sweeping health care act, which Mr. Romney had vowed to repeal. The law will now continue on course toward nearly full implementation in 2014, promising to significantly change the way medical services are administrated nationwide.
Confident that the economy is finally on a true path toward stability, Mr. Obama and his aides have hinted that he would seek to tackle some of the grand but unrealized promises of his first campaign, including the sort of immigration overhaul that has eluded presidents of both parties for decades.
But he will be venturing back into a Congressional environment similar to that of his first term, with the Senate under the control of Democrats and the House under the control of Republicans, whose leaders have hinted that they will be no less likely to challenge him than they were during the last four years.
The state-by-state pursuit of 270 electoral votes was being closely tracked by both campaigns, with Mr. Romney winning North Carolina and Indiana, which Mr. Obama carried four years ago. But Mr. Obama won Michigan, the state where Mr. Romney was born, and Minnesota, a pair of states that Republican groups had spent millions trying to make competitive.
Americans delivered a final judgment on a long and bitter campaign that drew so many people to the polls that several key states extended voting for hours. In Virginia and Florida, long lines stretched from polling places, with the Obama campaign sending text messages to supporters in those areas, saying: “You can still vote.”
UMA PRATAP SINGH
