COLUMBUS, Ohio — If one place is emerging as a test of Mitt Romney’s ability to capitalize on a new dynamic in the presidential race, it is Ohio, where he is intensifying his advertising, deploying more troops and spending four of the next five days.
Ohio, whose 18 electoral votes are critical to Mr. Romney’s candidacy, has bedeviled him like no other battleground state. His prospects were so shaky two weeks ago that his advisers openly discussed the narrow path to winning the necessary 270 electoral votes without Ohio, which every Republican president in the nation’s history has carried.
But as the race for the White House takes on a new air of volatility after President Obama’s off-kilter debate performance last week — a poll from the nonpartisan Pew Research Center on Monday suggested that Mr. Romney had wiped out the president’s lead among voters nationally — Mr. Romney is displaying new vigor in his fight for Ohio. The state, along with Florida, Iowa and Virginia, is now at the heart of his strategy for the remaining 28 days of the campaign.
Mr. Obama and Mr. Romney are both visiting Ohio on Tuesday, the final day of voter registration here, but Mr. Romney is sticking around for one of his most intensive bursts of campaigning yet. His increased presence is a response to pleas from state Republican leaders to invest more time and attention in the regions where he needs to turn out voters.
“Republicans who were concerned about some of the poll numbers now have a higher degree of enthusiasm,” said Senator Rob Portman, the chairman of Mr. Romney’s campaign here. “We’ve got a great opportunity to keep the momentum going.”
For the first time, Mr. Romney is personally making his case in a new television ad, saying, “Ohio families can’t afford four more years like the last four.” The message, while hardly novel, is welcome among Republicans who have watched with frustration as Mr. Obama’s campaign has dominated airwaves for weeks with a tailor-made operation in Ohio.
Mr. Romney’s problems here have included the Obama campaign’s success at defining him to many voters over the summer as an out-of-touch corporate raider, as well as a state economy that has been more vibrant than the country’s over all. With both the state and national unemployment rates now below 8 percent, Mr. Romney may have less opportunity than he did earlier this year to convince voters when he asks them in his new ad, “The question Ohio families are asking is ‘Who can bring back the jobs?’ ”
Several Republican officials, asked why Mr. Romney has been lagging well behind Mr. Obama, responded it was not because Mr. Romney was not selling here, but rather that his campaign had not been selling him well.
The president’s campaign has overwhelmed Mr. Romney until now in television advertising. In Youngstown, Mr. Romney and his allied groups ran virtually no advertisements through much of September, as Mr. Obama and his Democratic allies showed their ads more than 1,100 times, according to data compiled by the media monitoring firm Kantar Media/CMAG.
Mr. Romney has now increased his advertising in smaller markets across the state, including Youngstown, Zanesville and Lima. He is scheduled to travel the state on Tuesday and Wednesday with Gov. Chris Christie of New Jersey at his side, hoping to keep enthusiasm high among Republicans who have been showing up in greater numbers at volunteer centers across the state this week.
If the Romney campaign is to have a lasting resurgence in the four weeks until Election Day, his advisers say it must come in states like Ohio. But the presidential debate in Denver last week, where Mr. Romney commanded the stage, has provided him an opportunity to reset the contest.
The president’s advisers acknowledged in interviews that Mr. Romney was almost certain to get a “second look” from some Republican-leaning independent voters who had not yet embraced him despite misgivings about Mr. Obama, including in reliably Republican rural areas where Mr. Romney needs a large turnout.
A Republican-leaning voter in the Cincinnati area who was ambivalent about Mr. Romney before the debate said on Monday that she was now solidly on board.
“I was never really sure where he stood or who he was,” said the voter, Sara Campbell, 36, a mother of three. “To me, you have to be a strong leader in not only what you’re deciding, but also the way you come across.”
She added: “When he was right up against Obama, it really showed that he was strong, that he stands behind his convictions. And that was something that was important for me to see.”
Cathy Appel, 53, an independent voter from suburban Columbus, said she believed that Mr. Romney did a better job in the debate. But she said she was still leaning toward Mr. Obama because of Mr. Romney’s positions on women’s issues. “Mitt Romney came across much more confidently than I would have thought,” said Ms. Appel, a retired government worker. “But I can’t imagine selling myself down the river.”
Republican strategists in Ohio said Mr. Romney needed to increase his support among women, particularly in suburban areas. Requests from state Republicans for a television commercial featuring Ann Romney have not yet been approved by the campaign headquarters in Boston.
But Mr. Romney is now trying to focus his appeal to specific voters in each corner of Ohio, with a focus on coal production in the southeast, conservative values in the southwest and a bipartisan pitch in the suburbs of Cleveland. In that area, George V. Voinovich, a former senator and governor, declares in a new radio ad, “Mitt Romney will bring us together and end the divisiveness we have seen in Washington.”
The first polls since the debate last week suggest that enthusiasm and optimism are increasing among Republicans even as they send mixed signals about voter preferences in what has become a more fluid campaign.
The Pew Research poll on Monday found that Mr. Romney is backed by 49 percent of likely voters nationwide and that Mr. Obama is supported by 45 percent, which is within the poll’s margin of sampling error of plus or minus three percentage points for each candidate. But a Gallup survey of registered voters showed Monday that Mr. Obama is the choice of 50 percent and Mr. Romney of 45 percent.
Advisers to both campaigns said they needed to wait for more focus groups and polls to determine the state of the race. The president’s aides argued that, at best, Mr. Obama’s uneven debate performance hastened a tightening in polls that they said was going to happen this fall.
“We’ve always prepared for a close and competitive election, and we continue to,” Jim Messina, the president’s campaign manager, said in an interview.
The president continues to have more paths to reaching 270 electoral votes.
To win, Mr. Romney needs what some aides to Mr. Obama have been calling “an inside straight,” including winning Florida, Ohio, Virginia and either Colorado, Iowa or Nevada. But it is not a prospect that Democrats rule out, which is why Mr. Obama is scheduled to visit Ohio State University on Tuesday.
The president has spent considerable time on college campuses this fall, which was the subject of frustration on a recent morning in a conversation among party activists at a Republican Victory Center in Delaware County, just north of Columbus. Three volunteers, who were upbeat over last week’s debate, asked a reporter if Mr. Romney ever visited college campuses.
“He needs to campaign much harder,” said Jeff Edmister, 51, a Republican from nearby Westerville. “But thank goodness he’s starting to kick it up.”
Jeff Zeleny reported from Columbus, and Jim Rutenberg from New York.