U.S. President Barack Obama and Republican rival Mitt Romney are taking time off the campaign trail in secluded debate practice, underscoring the stakes for both in their first televised encounter Wednesday night.

Obama is at a resort in Henderson, Nev., while Romney was spending most of the day at a hotel on the outskirts of Denver, site of the first of their three debates in the next three weeks. With just five weeks until Election Day, they dispatched their wives and running mates to court voters in key states, such as the critical battleground of Ohio, where early voting began Tuesday. Balloting is already underway in other states.

Republican vice-presidential nominee Paul Ryan tried to invoke optimism as his ticket trails in the polls, and predicted the debates would spark a shift.

"Now we're entering what we call the debate and choice phase of this campaign," Ryan told The Jay Weber Show on Milwaukee's 1130 WISN talk radio. "People are going to focus on this. The debates are going to give us a chance to highlight our differences, and we're entering the phase where we get to frame the choice of this election."

Romney told thousands of cheering supporters after arriving in Denver on Monday that the debate is "not so much winning and losing or even the people themselves — the president and myself — it's about something bigger than that."

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He said he would get America working again. "Jobs is job one under my administration," Romney said.

His campaign also announced a new television commercial Tuesday that argues that Obama has raised taxes on the middle class while Romney will cut them. The ad is referring to the penalty under Obama's new health-care law against those who don't get health insurance.

Ryan, pressed for more specifics on how he and Romney would cut taxes without raising the deficit, said in an interview on Bloomberg TV that the details of how the cuts would be paid for would have to be worked out with Congress.

The Wisconsin congressman, who has his own debate with Vice-President Joe Biden next week, also said he hasn't gotten any advice from his predecessor, 2008 vice-presidential nominee Sarah Palin.

"I don't really know her. I met her once a few years ago," he told Bloomberg, adding that he hadn't really thought about what he would do differently than Palin. "What I would plan on doing is offering our alternatives, showing what we believe, how we are going to do things differently so the country has a very clear choice to make."

Ryan was set to visit three Iowa towns during a bus tour Tuesday, while Biden scheduled two events in North Carolina, another swing state. The president's wife, Michelle Obama, was campaigning in Ohio and Seattle, while Ann Romney was attending a rally in Littleton, outside Denver.

Both candidates on Monday reached out to Hispanic voters, a growing constituency in Colorado.

The White House said Obama will designate the home of labour leader Cesar Chavez as a national monument during a campaign swing through California next week.

Romney discussed immigration in an interview published Tuesday by the Denver Post, saying he would honour temporary work permits for young illegal immigrants who were allowed to stay in the U.S. because of action the Obama administration took this past summer.