One recent night, at a concert hall in San Francisco, Obama showed he can still whip 6,000 supporters into building cheers.
"I still believe in you. I'm asking you to keep believing in me," he declared. "I'm asking for your vote. I'm asking you to knock on doors. I'm asking you to make phone calls. And if you do, we will win this election. We'll finish what we started. And we'll remind the world why the United States of America is the greatest nation on earth."
The level of enthusiasm matters as each side tries to get as many of its supporters to the polls as possible. A big Republican enthusiasm advantage two years ago helped the GOP capture control of the U.S. House of Representatives in addition to making huge gains in statehouses across the nation.
For much of this year, Romney, the sometimes-stiff former businessman, has had a hard time generating the same electricity as Obama.
Indeed, most of the GOP's most passionate voters did not back Romney during the extended Republican primary season. His campaign typically favors made-for-TV invitation-only events where the emphasis is imagery — Navy ships, manufacturing plants, farm equipment — rather than crowd size. Audiences did increase as Romney began campaigning alongside running mate Paul Ryan, a favorite of the tea party, but he has generally struggled to get people excited on his own.
Until this week.
He drew an estimated 12,000 people to a central Florida rally last weekend, 1,200 to an Iowa town of just 1,000, and several hundred more to Newport News, Va., under heavy October rain.
"People wonder why it is I'm so confident we're going to win. I'm confident because I see you here on a day like this. This is unbelievable," Romney said, his wet hair stuck to the side of his face.
Soaked supporters standing in muddy puddles cheered as he delivered an abridged version of his standard campaign speech. Some wore ponchos, while many others stood shivering and drenched, hands in pockets.
At the Shelby County Fairgrounds, Judy Cartwright was wearing four layers to try to keep warm as the cold wind pushed temperatures into the 30s Wednesday night. It was Shelby's first glimpse of a presidential candidate since she met Harry Truman as an elementary school student more than six decades ago.
"At least it's not snowing," she said with a smile. "This is a chance of a lifetime."
AP White House Correspondent Ben Feller and Deputy Director of Polling Jennifer Agiesta in Washington and Bob Lewis in Richmond, Va., contributed to this report.