US Democrat Barack Obama will leave the presidential campaign trail to visit his ailing 85-year-old grandmother in Hawaii, whose health has deteriorated in recent weeks, an aide said on Monday.

With two weeks left in an intense battle for the White House, Obama will hold a campaign event in Indianapolis tomorrow and then fly to Hawaii to see his grandmother before returning to campaigning on Saturday, aide Robert Gibbs said.

"Senator Obama's grandmother, Madelyn Dunham, has always been one of the most important people in his life," Gibbs said in a statement. "Along with his mother and his grandfather, she raised him in Hawaii from the time he was born until the moment he left for college."

The campaign interruption comes as both candidates head into a final sprint for the November 4 election. Obama criticized Republican White House rival John McCain for a "say-anything, do-anything" political style as he launched a two-day tour to kick off early voting in Florida.

McCain told supporters in Missouri that "nothing is inevitable" and he could still beat Obama, who leads in national opinion polls as the pair began a frenzied race to the finish line.

Obama's former Democratic rival, New York Senator Hillary Clinton, joined the Illinois senator at a rally of 50,000 people in Orlando.

"In the final days of campaigns, the say-anything, do-anything politics too often takes over," Obama said. "We've seen it before. Hillary has been subject to it before.

"We're seeing again today - ugly phone calls, misleading mail and TV ads, careless, outrageous statements - all aimed at keeping us from working together, all aimed at stopping change," he said.

Obama noted McCain's running mate, Alaska Governor Sarah Palin, told reporters on Sunday that if she called the shots she would end the automated phone calls being made by McCain's campaign, including some that link Obama with 1960s radical Bill Ayers.

McCain defended the calls, shrugging off Palin's remarks in an interview.

"Well, Sarah is a maverick," McCain told CBS' "Early Show." "That robocall is absolutely accurate and by the way, Senator Obama's campaign is running robocalls as we speak."

Obama planned to spend two days in Florida to encourage voters to cast their ballots early in the battleground state, which has 27 electoral votes and is vital for either candidate in their quest for the 270 electoral votes needed to win the White House.

Standing on stage next to Obama, Clinton highlighted the financial crisis as she urged Florida voters to choose Obama.

It was the third time Clinton and Obama have campaigned together since he clinched the Democratic nomination in June.

A Reuters/C-SPAN/Zogby poll showed Obama with a 8-point edge on McCain. A new CNN poll, however, gave Obama a 5-point lead among likely voters, down from an 8-point edge two weeks ago.