By Charles Babington

NASHVILLE, Tenn. — Republican presidential candidate John McCain pledged Tuesday night in campaign debate to require the federal government to renegotiate the mortgages of individual homeowners and make them more affordable, a sweeping proposal to help families in the grip of a financial crisis.

“It is my proposal. It’s not Senator Obama’s proposal. It’s not President Bush’s proposal,” McCain said in the opening minutes of a 90-minute debate precisely four weeks before Election Day.

McCain’s Democratic rival, Barack Obama, said the current economic crisis was the “final verdict on the failed economic policies of the last eight years” that President Bush pursued and were “supported by Senator McCain.”

Obama said Bush, McCain and others had favored policies to deregulate the financial industry, wanting to “let markets run wild and prosperity would rain down on all of us. It didn’t happen.”

The two rivals debated on a stage at Belmont University in a race that lately has favored Obama, both in national polls and in surveys in pivotal battleground states.

The audience was selected by Gallup, the polling organization, and was split three ways among voters leaning toward McCain, those leaning toward Obama and those undecided.

Tom Brokaw of NBC, the moderator, screened their questions and also chose others that had been submitted online.

The two men also competed to demonstrate their qualifications as reformers at a time voters are clamoring for change.

McCain accused Obama of being the Senate’s second-highest recipient of donations from individuals at Fannie Mae and Freddie Mac, the two now-disgraced mortgage industry giants.

“There were some of us who stood up against this,” McCain said. “There were others who took a hike.”

Obama shot back that McCain’s campaign manager, Rick Davis, has a stake in a Washington lobbying firm that received thousands of dollars a month from Freddie Mac until recently.

Pivoting quickly to show his concern with members of the audience listening from a few feet away, he said, “You’re not interested in politicians pointing fingers. You’re interested in the impact on you.”

Leading in the polls, Obama hopes to cement his standing while McCain tries to turn his fortunes around.

Exchanges between the candidates have grown ever more acerbic with just four weeks to go until Election Day. Tuesday night’s debate gave McCain one of his last chances before a nationwide TV audience to halt the Democrat’s momentum and convince voters he is capable of addressing the crisis in the credit, housing and stock markets.

McCain’s running mate, Sarah Palin, has raised Obama’s ties to 1960s-era radical William Ayers and to the Democrat’s former pastor, the incendiary Rev. Jeremiah Wright. On Monday, McCain accused Obama of lying about the Republican senator’s record, and asked, “Who is the real Senator Obama?”

Obama’s campaign rolled out a video recounting McCain’s involvement in the 1980s Keating Five savings and loan scandal, while Obama himself accused McCain of engaging in “smear tactics” to distract from economic issues.

Both nominees have condemned character attacks in the past, and some supporters are urging them to cool the rhetoric.

McCain in June told reporters, “Americans are sick and tired of the personal attacks, the impugning of integrity” in campaigns.

Obama told an Iowa crowd in January: “We can’t afford the same old partisan food fight. We can’t afford a politics that’s all about tearing opponents down instead of lifting the country up.”

Some Republicans, while defending McCain’s recent tactics, feel he needs to engage voters on the issues, not character, to overtake Obama. Scott Reed, who managed Republican Bob Dole’s 1996 presidential campaign, said of the economic crisis: “McCain is suffering because Americans typically punish the party in power.”

McCain’s best bet, Reed said, is to show voters “who has the best solutions.”

Obama adviser David Axelrod told reporters the Democratic nominee wants to focus on economic issues but “we’re prepared for a very aggressive debate” if it becomes more personal. “We’re running for president of the United States,” he said. “It’s a rough, tough pursuit.”

The debate was being held at a time most Americans have a dismal view of the country’s direction.

A Gallup Poll released Tuesday showed just 9 percent say they’re satisfied with the way things are going, the lowest ever recorded in the 29 years Gallup has asked the question. Asked to name the country’s major problem, 69 percent said the economy. Next closest: 11 percent cited the Iraq war.