Republican John McCain and Democrat Barack Obama face off in their final debate on Wednesday, with McCain hoping a strong performance can begin to turn around a White House race that could be slipping away.
Three weeks before the Nov 4 election, McCain is running out of chances to reverse his slide in national opinion polls and gain ground on a surging Obama.
The 9 pm EDT (0100 GMT Thursday) encounter at Hofstra University in Hempstead in New York, will be the third and last debate between the presidential contenders and their final opportunity to reach a television audience of 60 million or more.
"You can do yourself a lot of good when you have a debate with that many people watching," South Carolina Republican Party Chairman Katon Dawson said.
The debate comes as new opinion polls show Obama gaining strength nationally and in battleground states after weeks of economic turmoil and plunging stock markets, with more voters saying they trust Obama's leadership on the economy.
A Reuters poll gave Obama a 4-point edge over McCain, but other national polls showed a larger margin for the Illinois senator. A CBS News/New York Times poll that showed Obama leading by 14 percentage points was the fifth survey this week to register Obama's lead in double-digits.
The bad poll news heightened the debate stakes for McCain, who unveiled a package of measures on Tuesday to help investors, particularly older Americans, who have seen their retirement savings decimated by stock market losses.
But McCain also said he was not finished talking about Obama's service on a community board in Chicago with former 1960s radical William Ayers. The Arizona senator said he was likely to talk about Ayers during the debate.
Ayers was not discussed in the last debate, although McCain had been talking about him on the campaign trail. After the last debate, Obama noted McCain's reluctance to discuss the issue with him directly.
'DIDN'T HAVE THE GUTS'
"I was astonished to hear him say that he was surprised that I didn't have the guts to do that," McCain said in an interview with KMOX radio in St. Louis, Missouri. "I think he's probably assured that it's going to come up this time."
Several recent polls have shown McCain's attacks on Obama's character largely backfired, increasing unfavorable opinions about McCain among voters looking for solutions on the economy.
"There is no question the negative campaigning just isn't working," pollster John Zogby said. "To make an impact in this debate, McCain needs to be proactive and be very specific about the way he would lead an economic recovery."
Both candidates spent time on Tuesday cramming for the showdown. Obama holed up at a secluded resort on Lake Erie in the battleground state of Ohio, while McCain rehearsed at a stage complex in New York's theater district.
At a New York fundraiser with running mate Sarah Palin on Tuesday night, McCain quipped to cheering supporters: "I want to do about half as good as Sarah did against poor old Joe Biden."
Polls showed most voters thought Biden, a Delaware senator and the Democratic vice presidential nominee, outperformed the first-term Alaska governor in their lone debate.
The presidential debate will focus on domestic policy and the economy. Obama and McCain will be seated at a table with moderator Bob Schieffer of CBS News instead of standing at podiums as in the first debate.
That could provoke more direct exchanges than in the first two encounters, which did little to recast the presidential race. McCain needs a sharper performance to build momentum for the final 2 1/2 weeks on the campaign trail.
"He has time to come back in this race," Dawson said of McCain. "Every day is a lifetime in American politics. But he has to get started."