As Democratic presidential candidate Barack Obama launched a multi-million dollar media blitz projecting himself as an agent of age in the final days of the campaign, Republican rival John McCain questioned Obama's ability to lead.
With six days to go for the Nov 4 poll, Obama's campaign spent more than $3 million to air a 30-minute infomercial on seven networks simultaneously as the White House race tightened to three points Wednesday in major opinion polls.
Several polls including Rasmussen and Gallup polls, each of which had Obama up five points a couple of days ago, now have him 50 to 47 percent ahead. Obama still leads by five to six points among independents, but 18 percent of them remain undecided.
Obama appeared at one Florida rally with his running mate, Joseph R Biden, and another with former president Bill Clinton as local news shows went live in the crucial battleground state.
The campaign also unleashed its first advertisement critical of Republican vice presidential candidate Sarah Palin as Obama addressed big crowds in Florida and North Carolina, where he hopes to snap a Republican run.
In a day capped with a taped interview on Comedy Central's "The Daily Show", the Democrat also cautioned his supporters against overconfidence despite his lead in most polls. He told them: "Don't believe for a second this election's over."
In the 30-minute advertisement, which McCain dismissed as a "gauzy, feel-good commercial", Obama aimed to etch a portrait as a candidate who understands the economic toll the nation is enduring and who would turn the page on the current administration.
He introduced voters - a group carefully selected by his campaign that cut across geography and racial lines - and discussed their struggles with mortgage payments, access to health care and fears of a losing a job.
The programme ended with two minutes of live footage of Obama speaking to 20,000 cheering supporters in South Florida, where he hopes to stockpile votes in a state in which polls show him with a slender advantage.
As the national audience tuned in, Obama said: "In six days, we can choose hope over fear and unity over division. The promise of change over the power of the status quo."
Likening Obama to an infomercial salesman, McCain told a crowd in Riviera Beach, Florida: "He's offering government-run health care, an energy plan guaranteed to work without drilling... and an automatic wealth-spreader that folds neatly and fits under any bed."
Sharpening his critique of Obama's ability to serve as commander in chief, he argued in a speech in Tampa that the Democratic nominee's economic policies would "undermine our national security" and in a "Democratic-dominated Washington", national security and the economy would both suffer.
"Raising taxes and unilaterally renegotiating trade agreements as they have promised would make a bad economy even worse, and undermine our national security, even as they slash defence spending," McCain said.
The Republican National Committee also issued ads that called Obama unready for the White House. One called him "risky".
Another airing frequently in North Carolina shows stormy seas and asks: "What if this storm does get worse?"
A McCain spot argued that the Democrat is not ready for the White House "yet". The ad also mocks Obama's Internet-savvy campaign by finishing with the words, "Barack Obama: untested".