NASHVILLE, Tenn. --Tonight, Arizona Sen. John McCain finally gets his town hall.

More than a year ago, when his all-but-broke campaign was laying off staffers across the country, the Republican senator vowed to revive it with town hall appearances up and down the state of New Hampshire. To general surprise, his prediction proved accurate.

Now, with his general election campaign lagging in key state polls, Mr. McCain gets another chance to revive his campaign tonight in Nashville, as he confronts Illinois Sen. Barack Obama face to face in the format the Republican likes best.

Mr. McCain, in fact, once proposed that the two candidates face each other as many as 10 times in town hall debates. But as economic uncertainty preoccupies voters and helps push them toward his Democratic rival, the odds facing Mr. McCain's challenge are again daunting.

The rivals' Tennessee encounter comes after days in which both campaigns have taken on harsher, more personal tones, in person and on the airwaves. Recognizing that the economy is an issue that plays to Mr. Obama's strengths, the Republican campaign has tried to shift the campaign focus to spotlight the Democrat personally.

At a rally yesterday in Albuquerque, N.M., Mr. McCain raised pointed questions about his opponent's character and truthfulness.

"Rather than answer his critics, Senator Obama will try to distract you from noticing that he never answers the serious and legitimate questions he has been asked," Mr. McCain said. "But let me reply in the plainest terms I know: I don't need lessons about telling the truth to American people. And were I ever to need any improvement in that regard, I probably wouldn't seek advice from a Chicago politician. Senator Obama has accused me of opposing regulation to avert this crisis. I guess he believes if a lie is big enough, and repeated often enough, it will be believed."

Mr. McCain's criticism of the Democrat continued as he scored Mr. Obama for having called the move to promote sub-prime mortgages "a good idea" in a speech last year.

The Obama camp responded that the Republican had taken that quote out of context, pointing out that, in the speech, the Democrat had said the riskier loans had started out as a good idea, but one that was then subverted by reckless business practices and an absence of regulation.

The GOP nominee's tough words were a sequel to similarly sharp attacks from his running mate, Alaska Gov. Sarah Palin. Yesterday and over the weekend, she reminded voters of the Illinois Democrat's past associations with William Ayers, a Chicago educator who is a former member of the Weather Underground. And, responding to a question in an interview with William Kristol, a New York Times columnist, Ms. Palin agreed that Mr. Obama's links to his former pastor, the Rev. Jeremiah Wright, should also be open to campaign scrutiny.

Not to be left behind in this ad hominem arms race, the Obama campaign responded with an assault on Mr. McCain's past. The campaign directed its supporters to an Internet video that disinterred questions about the Arizona senator's role 17 years ago as one of the Keating Five, a congressional scandal during the nation's savings-and-loan industry financial crisis.

Mr. McCain was among five senators investigated by a Senate ethics panel over charges that they had improperly pressured regulators to go easy on the S&L operations of Charles Keating, then a close associate of Mr. McCain. In contrast to three of his colleagues, the panel exonerated Mr. McCain of wrongdoing, but said he had exercised poor judgment in his contacts with regulators.

While his campaign joined in the acrimonious back-and-forth, Mr. Obama, campaigning in North Carolina, called his opponents' attacks an effort to distract voters from the state of the economy.

"I cannot imagine anything more important to talk about than the economic crisis," he said, "and the notion that we'd want to brush that aside and engage in the usual political shenanigans and scare tactics that have come to characterize too many political campaigns, I think is not what the American people are looking for."

At the same time, the Republican campaign released a new commercial calling Mr. Obama "dangerous" and "dishonorable" because of a statement in which he had questioned U.S. tactics in Afghanistan. And, taking a page from the traditional GOP playbook, the Democrat's commercials assailed Mr. McCain as a tax raiser because of an element in his health plan that would remove the tax preference for employer-paid health benefits.

While the rhetoric was harsh on both sides on the eve of the second of the presidential candidates' three debates, it was unclear how much would impress voters on a day when the news was dominated by new hammer blows to world credit markets.

The candidates' first debate occurred in the foreground of another chapter of the economic maelstrom -- the struggle to get Congress to ratify a rescue package for Wall Street. Surveys found that more voters thought the Democrat had won the debate. Mr. Obama's poll numbers have steadily climbed in the days since, whether because of a steady performance in that debate or because of the continuing preoccupation with an issue that is ripe for Democratic criticism in the eighth year of Republican administration.

The pressure on Mr. McCain to refocus the race is clear. In a conference call with reporters last week -- on the same day the GOP camp acknowledged that it was effectively ceding one battleground state, Michigan, to the Democrats -- a McCain strategist argued that the campaign was competitive enough in other battlegrounds to put their man in the neighborhood of 260 electoral votes, just short of the 270 needed for election.

"We are currently competing aggressively in Minnesota, Iowa, Wisconsin, Colorado, Pennsylvania, Nevada, New Hampshire and New Mexico," McCain strategist Greg Strimple said. "The combination of any of those states -- we have to get 10 more electoral votes in order to be successful, and have Mr. McCain as the next president of the United States."

But that is a precarious strategy for the Republican. Mr. McCain has described himself as a gambler, and his hopes of prevailing next month amount to a multi-card draw to an inside straight. Or, to borrow a metaphor from a sport favored by Mr. Obama, Mr. McCain -- with no margin for error -- must run the electoral table described by his aide.

Polls continue to suggest that will not be easy. In Minnesota -- the GOP convention's site and a state that had been consistently close -- one new survey, from the Minneapolis Star-Tribune, shows Mr. Obama leading by a landslide, 55 percent to 37 percent, although another, by SurveyUSA, depicted the state's race as a dead heat. In Ohio, a state whose loss would be fatal to Mr. McCain's chances, several new polls have also showed Mr. Obama moving into a lead.

In New Hampshire, a state that had been considered a toss-up, where lots of independent voters have voted for Mr. McCain in his two primary victories, a New Hampshire Institute of Politics poll put Mr. Obama's lead at 49 percent to 37 percent. New polls in two traditionally Republican states, North Carolina and Virginia, also showed Mr. Obama moving into significant leads.

And in Pennsylvania, a tracking poll conducted for the Allentown Call by Muhlenberg College showed Mr. Obama ahead, 49 percent to 38 percent.

All those circumstances combine to suggest that Mr. McCain will be under pressure to sustain his aggressive focus on his foe in hopes of shaking up the dynamics of their competition.

But neither candidate will be in complete control of today's encounter at Nashville's Belmont University, in which questions will come from supposedly undecided voters selected by the bipartisan debate organizers.

After trying to persuade them, and the television audience beyond, Mr. McCain will switch his sights to Pennsylvania's voters tomorrow, when he and his running mate travel to a rally at Bethlehem's Lehigh University.