The New York Times has a good piece on how the President clawed back in the final month of campaigning after a miserable showing in the first debate:
Mr. Obama, who had dismissed warnings about being caught off guard in the debate, told his advisers that he would now accept and deploy the prewritten attack lines that he had sniffed at earlier. “If I give up a couple of points of likability and come across as snarky, so be it,” Mr. Obama told his staff.
As his campaign began an all-out assault on Mr. Romney’s credibility and conservative views, the president soon was denouncing Mr. Romney’s budget proposals as a “sketchy deal” and charging that the Republican nominee was not telling Americans the truth.
Mr. Obama recognized that to a certain extent, he had walked into a trap that Mr. Romney’s advisers had anticipated: His antipathy toward Mr. Romney — which advisers described as deeper than what Mr. Obama had felt for John McCain in 2008 — led the incumbent to underestimate his opponent as he began moving to the center before the debate audience of millions of television viewers.
By the end of the 30 days, after Air Force One carried Mr. Obama on an almost round-the-clock series of rallies, the president had reverted back to the agent of change battling the forces of the status quo, drawing contrasts between himself and Mr. Romney with an urgency that had been absent earlier in the race. Mr. Obama had returned, if not to the candidate that he was in 2008, as a man hungry for four more years to pursue his agenda in the White House.
Not to be discounted: Hurricane Sandy and Romney’s (negative) portrayal of federal relief in national disasters.