Republican John McCain questioned Democratic rival Barack Obama's readiness for the White House and Obama planned a prime-time television appeal as a bruising presidential battle hit the final stretch.
McCain kicked off a tour of the must-win state of Florida with a warning that Democratic control of the White House and Congress would be bad news for small businesses and American workers.
"The answer to a slowing economy is not higher taxes, but that is exactly what is going to happen when the Democrats have total control of Washington. We can't let that happen," McCain told supporters at a rally in Miami, Florida, six days before the vote.
McCain has charged that Obama's plans to raise taxes on those making more than ,000 would hurt small businesses, saying Obama wants to be "Redistributor in Chief".
"Senator Obama is running to spread the wealth. I'm running to create more wealth. Senator Obama is running to punish the successful. I'm running to make everyone successful," McCain said.
Obama, who has proposed tax cuts for lower- and middle-income workers, said McCain's economic policies would be bad news for the middle class and would mean more of the Republican approach followed by President George W Bush.
"He's spending these last few days calling me every name in the book. I'm sorry to see my opponent sink so low," Obama said in remarks prepared for delivery in Raleigh, North Carolina.
"So let's cut through the negative ads and the phony attacks - under John McCain, the middle class will watch wealth get favored over work, jobs get shipped overseas, and the cost of health care and college go through the roof," he said.
McCain is struggling to overtake Obama's lead in national polls and to defend about a dozen key battleground states won by Bush in 2004, with Florida and its 27 electoral votes leading the list.
A Reuters/C-SPAN/Zogby poll showed Obama with a 5-point national lead on McCain. A blizzard of recent national polls gave Obama a national lead ranging from 2 points to 15 points.
But the key for both candidates is winning the 270 electoral votes needed to capture the White House, and Florida is a big piece of the puzzle.
A win in Florida for Obama, who earlier this month sent two of his top campaign officials to the state to supervise the voter turnout effort, could clinch the White House for him.
"We need to win in Florida," McCain, an Arizona senator, said in Miami. Polls show the two candidates running about even or Obama slightly ahead in the state that decided the 2000 election after a disputed recount.
Obama also planned a visit to Florida, where he will make his first joint campaign appearance with former President Bill Clinton at a late-night rally in Orlando after an expensive prime-time television address on three networks.
Obama, whose fundraising juggernaut has broken all records and allowed him to blanket battleground states with ads, has purchased 30 minutes of time on CBS, NBC and Fox for an extended pitch on his economic plans.
The ad, which costs about million for each network, coincides with the anniversary of the October 29, 1929, "Black Tuesday" stock market crash that ushered in the Great Depression.
Obama has surged in the last month in conjunction with the Wall Street economic crisis, with polls showing voters prefer his approach to turning around the economy.
McCain has tried to paint Obama, a first-term senator from Illinois, as too inexperienced to trust in the Oval Office, and he released another advertisement expanding on the theme.
"Behind the fancy speeches, grand promises and TV special lies the truth - with crises at home and abroad, Barack Obama lacks the experience America needs," the narrator said.
McCain also renewed his call for the Los Angeles Times to release a videotape of a 2003 banquet where Obama spoke of his friendship with Rashid Khalidi, a leading Palestinian scholar and activist. Also present was William Ayers, a former 1960s radical who Obama served with on a community board in Chicago.
The Times reported on the contents of the tape in an April 2008 story about Obama's ties with Palestinians and Jews, but says it cannot release the tape because it was obtained from a source on the promise it would not be released to the public.
"Now why that should not be made pubic is beyond me. I guarantee you, if there was a tape with me and Sarah Palin and some neo-Nazi or one of those, you think that that tape wouldn't be made public?" McCain said in a radio interview.
McCain's running mate Sarah Palin, the governor of Alaska, warned that Americans should not let up in the quest for more energy independence just because the cost of oil has dropped below a barrel.
"Though this sudden drop in prices sure makes a difference for families across America, the dangers of our dependence on foreign oil are just as they were before," Palin said in Toledo, Ohio.