WASHINGTON (AP) — President Barack Obama, locked in a fierce re-election bid, is emphasizing his incumbent's role for a third straight day, skipping battleground states to visit victims of Hurricane Sandy in New Jersey, a state he's confident of winning. The president's actions have forced his Republican challenger, Mitt Romney, to walk a careful line and make tough choices.

The former Massachusetts governor must show respect for the superstorm's casualties all along the Eastern Seaboard. But Romney can ill afford to waste a minute of campaign time, with the contest virtually deadlocked in several key states and the election six days away.

After tamping down his partisan tone Tuesday at an Ohio event that chiefly emphasized victims' relief, Romney planned three full-blown campaign events Wednesday in Florida, the largest competitive state. Sandy largely spared Florida, so Romney calculates he can campaign there without appearing callous.

Obama's revised schedule is a political gamble, too. Rather than use the campaign's final Wednesday to woo voters in tossup states, he will go before cameras with New Jersey's Republican governor, Chris Christie. Christie is one of Romney's most prominent supporters, and a frequent Obama critic. But Christie praised Obama's handling of superstorm Sandy, a political twist the president's visit is sure to underscore.

Obama also took full advantage of incumbency Tuesday. He visited the Red Cross national headquarters — a short walk from the White House — to commiserate with victims and encourage aid workers.

"This is a tough time for millions of people," the president said. "But America is tougher."

While Obama and Romney moved cautiously Tuesday, their campaigns exchanged sharp words in Ohio and expanded their operations into three Democratic-leaning states, a move that will reshape the contest's final six days.

Romney's campaign is running ads in Minnesota and Pennsylvania, and a pro-Romney group is doing the same in Michigan. The three states were considered fairly safe for Obama, but his campaign is taking the threat seriously. It sent former President Bill Clinton to Minnesota on Tuesday and it is buying airtime in all three states.

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Republican strategists differ on the Romney campaign's thinking. Some think Romney's aides fear losing all-important Ohio, and they hope for a stunning last-minute breakthrough elsewhere to compensate. Others say the GOP camp has so much money — and so few chances to buy useful airtime in saturated states — that it can spend millions of dollars on a long shot without scrimping in a battleground.

"If they didn't have so much money, they wouldn't be able to do something with so little chance of success," said Democratic strategist Tad Devine.

Some Republicans played down the significance of the expand-the-map strategy.

"This always happens this time of year" in a big campaign, said Republican consultant Mike McKenna of Richmond, Va. "They see a poll or two" that suggests a sudden tightening of the race in a place like Minnesota "and they get all excited."

"They tend to chase shiny objects," McKenna said. Ohio, he said, remains by far the most important state for Romney to win.

Another sign that Ohio looms large for the Romney campaign: a guest-filled rally in suburban Cincinnati on Friday to kick off the campaign's final four days. Set to join the GOP ticket are golf legend Jack Nicklaus, former Secretary of State Condoleezza Rice, Texas Gov. Rick Perry and former New York City Mayor Rudy Giuliani.

Meanwhile, Democratic groups bitterly complained about a TV ad the Romney camp is running in the Toledo and Youngstown areas of Ohio. The ad suggests that Jeep will move its Toledo car-making facility to China, a claim Jeep executives deny.

Democrats called the ad a brazen lie and a sign of desperation. Even some Republicans worried that Romney has gone too far in a state where voters follow the auto industry closely.

"It's the kind of thing that happens late in the campaign, when everybody's tired and you're not quite yourself," McKenna said. "It didn't help. But I don't think it's a big thing. At this point, everybody has made up their mind."

Vice President Joe Biden planned to campaign Wednesday in Florida. Romney's running mate, Rep. Paul Ryan, was scheduled to campaign in his home state, Wisconsin.

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Associated Press writer Thomas Beaumont in Des Moines, Iowa, contributed to this report.