Democrat Barack Obama will leave the White House trail later this week to dash to the side of his gravely ill 85-year-old grandmother in Hawaii, just 11 days before the election.
The Illinois senator will cancel events in midwestern Iowa and Wisconsin and head to his native Hawaii for a one-day trip on Thursday, before throwing himself back into full bore campaigning on Saturday, advisor Robert Gibbs said.
Obama's grandmother Madelyn Dunham played an instrumental role in his upbringing and he lauded her as an anchor of his life in his convention speech in August.
"In the last few weeks her health has deteriorated to the point where her situation is very serious," Gibbs told reporters on Obama's plane in Florida, while declining to give further details of Dunham's condition.
"It is for that reason Senator Obama has decided to change his schedule on Thursday and Friday so that he can see her and spend some time with her. He will be returning to the campaign trail on Saturday."
"Senator Obama's grandmother Madelyn Dunham has always been one of the most important people in his life," Gibbs said.
"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," Gibbs said.
"As he said at the Democratic convention, she poured everything she had into him."
Obama has a healthy lead in polls in Iowa and Wisconsin, so cancelling stops in the two states would not seem to pose too much of a risk politically. He will add a stop in swing state Indiana on Thursday before heading to Hawaii.
Earlier, Obama accused Republican John McCain of launching an "ugly" bid to stave off defeat as he blitzed the crucial swing state of Florida, where early voting opened on Monday, with onetime foe Hillary Clinton.
"In the final days of campaigns, the say-anything, do-anything politics too often takes over," Obama said in Tampa.
"We've seen it before and we're seeing it again -- ugly phone calls, misleading mail, misleading TV ads, careless, outrageous comments," Obama said.
"It's getting so bad that even Senator McCain's running mate denounced his tactics last night ... You really have to work hard to violate Governor Palin's standards on negative campaigning."
Sarah Palin, who has launched some of the most stinging attacks against Obama, said Sunday that if she were in charge, she would not rely on "the old conventional ways of campaigning, that includes those robo-calls."
The McCain campaign has been using automated calls to question Obama's character and values in a bid to drive up his negative ratings in swing states.
Obama, meanwhile was basking in his high-power endorsement by former Republican secretary of state Colin Powell and the news that he raked in a staggering 150 million dollars in fundraising in September.
The Democrat leads national polls and appears to be in a position to squeeze McCain across the electoral map, with time running out for the Republican to launch a comeback.
But McCain, following Obama's weekend footsteps to the midwestern battleground state of Missouri, warned "nothing is inevitable" despite his huge cash deficit and polls which give Obama the lead two weeks out.
"We never give up, we never quit," the Arizona senator told cheering supporters and accused Obama of wanting to "redistribute wealth."
McCain warned voters that Obama "won't have the right response" to crises which emerge on the world stage and is planning to "raise taxes, increase spending, and concede defeat in Iraq."
"The next president won't have time to get used to the office. We face many challenges here at home, and many enemies abroad in this dangerous world," McCain told a rally in Belton, Missouri.
"What America needs in this hour is a fighter; someone who puts all his cards on the table and trusts the judgment of the American people."
Clinton, appearing at a rally with Obama on a balmy evening in Florida, said McCain just represented an extension of the presidency of George W Bush.
"We are in an economic crisis born and bred by the failed Republican policies of George Bush and John McCain.
"George Bush has practiced what John McCain has preached."
The latest daily tracking poll of registered voters by Gallup showed Obama expanding his lead to 11 points nationwide. The daily Rasmussen survey, however, had McCain narrowing the race to four points, trailing Obama by 50 per cent to 46 per cent of voters nationwide.