Senator and Senator entered their general election contest this summer denouncing American politics as trivial and negative, and vowing to run campaigns that would address the concerns of voters during a difficult time.
But Mr. McCain made clear on Monday that he wanted to make the final month of the race a referendum on Mr. Obama’s character, background and leadership — a polite way of saying he intends to attack him on all fronts and create or reinforce doubts about him among as many voters as possible. And Mr. Obama’s campaign signaled that it would respond in kind, setting up an end game dominated by an invocation of events and characters from the lives of both candidates.
The change in tone formed a backdrop for the nationally televised debate between the two candidates on Tuesday night, the second of their three scheduled encounters. It comes when Mr. McCain is under increasing pressure to do something to turn around his campaign, with polls giving Mr. Obama an advantage in the race and in who Americans trust more to deal with the economy, the issue that now trumps all concerns.
Yet in shifting toward a more negative and personal message, the two campaigns risked seeming detached from the economic anxieties of voters at a time when the financial system is teetering. The risk could be especially great for Mr. McCain, who has ceded political ground to Mr. Obama during the financial crisis and has taken the more combative stance in recent days. A lacerating speech he gave Monday — “Who is the real Barack Obama?” Mr. McCain asked — was shown on cable television juxtaposed with images of another horrible day on Wall Street.
“Whatever the question, whatever the issue, there’s always a back story with Senator Obama,” Mr. McCain said, speaking in Albuquerque. “My opponent’s touchiness every time he is questioned about his record should make us only more concerned.”
During the day, Mr. McCain’s running mate, Gov. , raised questions about Mr. Obama’s “truthfulness and judgment.” Mr. McCain’s supporters sought to focus attention on Mr. Obama’s associations with his former pastor and a onetime 1960s radical. The called for an investigation into questionable campaign contributions to Mr. Obama.
Mr. Obama’s campaign responded by releasing a slick, 13-minute video describing Mr. McCain’s connections with the scandal that tarnished Mr. McCain during the 1980s, a video that Mr. Obama’s advisers said had been held in wait in case this moment arrived. Mr. Obama’s aides portrayed Mr. McCain as angry and impetuous. Mr. Obama scolded his opponent as trying to turn attention away from the economy.
“I cannot imagine anything more important to talk about than the economic crisis,” Mr. Obama said, campaigning in Asheville, N.C. “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.”
Mr. McCain’s aides suggested the attacks that he and his running mate had unleashed were intended to set the table for their debate in Nashville, one of the few high-profile moments Mr. McCain has left to reach voters across the country and present a disqualifying version of Mr. Obama. Ms. Palin told a crowd in Florida that she had advised Mr. McCain to “take the gloves off” on Tuesday night.
Still, it may not be easy: This debate will be in a town-hall setting and the candidates will be taking questions from voters, a format that historically has made it difficult to mount the kind of attacks Mr. McCain is looking to make.
Ms. Palin again invoked Mr. Obama’s sporadic encounters with William Ayers, a founder of a 1960s radical group — amplifying a message the McCain campaign was pushing in a steady stream of e-mail messages to reporters and supporters — and suggested again that Mr. Obama was “not one of us.”
At a rally in Estero, Fla., for Ms. Palin, one of the introductory speakers, Mike Scott, the sheriff of Lee County, referred to the Democratic candidate as Mr. Obama as “Barack Hussein Obama.”
In an interview with on the Op-Ed page of The New York Times on Monday, Ms. Palin suggested that it would be fair for Mr. McCain to invoke Mr. Obama’s relationship to his former pastor, the , given the incendiary nature of Mr. Wright’s views — even though Mr. McCain has condemned some previous attacks on Mr. Obama linking him to Mr. Wright.
Strategists from both parties suggested that this kind of turn in tone was inevitable.
“There are not a lot of things we can count on these days,” said Mark McKinnon, a former adviser to Mr. McCain who stepped aside earlier this year because, he told associates, he did not want to be part of a campaign tearing down Mr. Obama. “But, the sun will rise. The sun will set. And presidential campaigns will go negative.”
Chris Lehane, a Democratic consultant known as an advocate for tough campaigns, said: “At the end of the day, campaigns are campaigns. In the last five days, it always comes down to a knife fight in a telephone booth.”
But several strategists, including Republicans, questioned whether this tactic would be successful for Mr. McCain, given the lateness of the date and the economic crisis washing over the country.
“This is not a normal campaign. Normal personal or character-based attacks are not going to work particularly well,” said Stuart Stevens, a Republican consultant who worked for President Bush’s re-election campaign in 2004. “If your house is on fire, all you care about is who can put the fire out the best.”
, a senior aide to Senator during her tough fight against Mr. Obama in the Democratic primaries, had long warned that Mr. Obama’s history with Mr. Ayers would provide fodder to Republicans. But Mr. Wolfson said Monday that he did not think it would be effective in this environment, coming so late and at a time of such anxiety about the economy.
“It might have made a difference had the financial underpinning of the country not just collapsed,” he said. “You’re not going to change the subject from the economy.”
Ms. Palin has several times cited a New York Times article published Saturday in raising Mr. Obama’s association with Mr. Ayers, but she has sidestepped its conclusion that the two men did not appear to be close and that Mr. Obama had never expressed sympathy for the radical views and actions of Mr. Ayers.
Mr. Obama left it to his surrogates to raise the Keating bank scandal, as he talked about the economy and argued that Mr. McCain was running away from the subject; his aides suggested this would be the tack he would take at the debate.
Yet if Democrats were once concerned — and they were — that Mr. Obama or his campaign did not have the stomach to push back in this kind of fight, the aggressive response by the campaign and the candidate might well have assuaged it. The language out of the Obama campaign — in advertisements, statements and remarks by surrogates — was filled with language intended to underline Mr. McCain as hotheaded.
“Look, I’m not sitting here with my feet up,” said David Axelrod, Mr. Obama’s senior political adviser. “I think we have to fight. This is going to be a struggle every day.”
Mr. McCain’s chief strategist, , did not respond to an e-mail message requesting comment.
Julie Bosman, Patrick Healy and Kitty Bennett contributed reporting.
This article, "," first appeared in The New York Times.