"Hope was restored in 90 minutes," said Steve Schmidt, campaign manager for 2008 GOP nominee John McCain.
Many activists wish it had come sooner. Obama's experienced voter-turnout operation already is marching supporters by the thousands to early polling sites in Iowa, North Carolina and Ohio, the most fiercely contested state of all.
If the election were today, Obama probably would carry Ohio, making Romney's path to the 270 needed electoral votes extremely narrow. Public and internal polls show Obama ahead by 5 to 8 percentage points.
Romney's campaign on Friday began airing an ad, "Ohio Jobs," in which Romney speaks directly to the camera. Democrats hope Friday's jobs report will make the ad sound off-message to many Ohioans.
In Virginia, a traditionally Republican state until Obama won it four years ago, the race is tighter, although the president is seen with the advantage. After the debate, Romney went straight to Virginia, where he and running mate Paul Ryan headlined a rally in the state's conservative west.
There was anecdotal evidence in some states that Romney's debate job was bringing in new donations and volunteers.
"I've been in Daytona, Flagler County and St. John's County, and all over, people are asking for signs, asking for bumper stickers, some of them are even asking where they can send money," said Florida state Sen. John Thrasher, a former state GOP chairman. "The energy level is fantastic."
In Nevada, where Romney has not led in any publicly released poll, new volunteers showed up at GOP offices.
Gustavo Guadamud, 31, had planned to vote for Romney, but after watching the debate he decided it was time to do more.
"A lot of people thought that he doesn't have what it takes," Guadamud said. "But every time President Obama was replying, he looked him right in the eye."
Guadamud, a web designer, had intended to leave a small donation at the Romney office and pick up a bumper sticker. He ended up phoning registered voters for two hours.
Babington reported from Washington. Associated Press writers Nicholas Riccardi in Nevada and Brendan Farrington in Florida contributed to this report.
- Live at the GOP convention: Donald Trump...
- Cruz: Not supporting candidate who wages...
- Rupert Murdoch vows Fox News without Ailes is...
- NBA moving All-Star Game out of Charlotte,...
- Kaine emerges as a favorite in Clinton's VP...
- Hundreds of demonstrators gather on...
- Fox needs to find a successor to man who...
- Brazil nabs 10 IS backers in Olympics...
- Utah delegates finally stand and cheer... 93
- Obama rejects Trump depiction of US in... 41
- The day after: Lee defends Cruz at GOP... 32
- Police give all-clear in Munich... 31
- Dems' division, emails roil party on... 28
- In wake of email hack, Democratic chair... 23
- Daughter Ivanka Trump raises issues... 21
- NBA moving All-Star Game out of... 20