WASHINGTON (AP) — Mitt Romney’s running mate shot down the need for a breakthrough in the first presidential debate Wednesday, trying to allay Republican concerns that the race is slipping away with five weeks to go and momentum on President Barack Obama’s side.

Vice presidential nominee Paul Ryan, working to keep debate expectations for Romney in check, praised Obama’s debating skills and called the Democratic incumbent ‘‘a very gifted speaker’’ with years of experience on the national stage. He played down signs that Obama is gaining distance in the most competitive states. Polls are tight, Ryan said, and will stay that way until the election Nov. 6.

‘‘We’re running against an incumbent president with incredible resources,’’ Ryan said. ‘‘More importantly, I don’t think one event is going to make or break this campaign.’’

At a rally in Las Vegas Sunday, President Barack Obama was tamping down expectations himself, downplaying his own oratorical skills while praising Romney's.

‘‘Gov. Romney, he’s the debater. I'm just OK,’’ Obama said.

Earlier Sunday a prominent Romney supporter said he expected Romney’s performance in Denver on Wednesday night would shake up the campaign after a ‘‘tough couple of weeks.’’ Gov. Chris Christie, R-N.J., predicted Romney would do ‘‘extraordinarily well’’ in the debate, and that come Thursday morning, ‘‘this whole race is going to be turned upside down.’’

Romney is trying to rebound from a difficult September, and the three October debates offer a chance to help show that the race is winnable. Christie, who passed on a 2012 run for the White House but is a possible contender in 2016, called the domestic policy and economic debate in Denver ‘‘the restart of this campaign.’’

That confidence from a high-profile backer comes even as Americans are growing more optimistic about the economy and Obama’s leadership, creating a significant obstacle for Romney.

Polls show Obama with a steady lead in many of the nine states where the candidates are competing most fiercely. If the election were held today, an Associated Press analysis shows Obama would win at least 271 electoral votes, enough for re-election. The analysis is intended to provide a snapshot of a race that until recently has been stubbornly close in the small number of the most contested states.

At an evening rally in Las Vegas, the president said that while some people might be focused on who has the best ‘‘zingers’’ in the debate, he was focused on having a serious discussion about the nation’s future.

‘‘That is what people are going to be listening for,’’ he said. ‘‘That’s the debate you deserve.’’

Obama drew more than 11,000 people to the evening rally in the Western battleground state. The event was aimed in part at boosting enthusiasm among Hispanics, a key source of support for Obama in Nevada. The popular Mexican rock band Mana performed ahead of the president’s remarks.

Obama is staying in Nevada as he prepares for the debate. Accompanying him was a cadre of advisers assisting with debate prep, including chief of staff Jack Lew, top economic adviser Gene Sperling, pollster Joel Benenson and speechwriter Jon Favreau. Sen. John Kerry, D-Mass., who is playing Romney in debate prep, was traveling to Nevada separately.

Romney remained in Boston on Sunday, going through preparations of his own for Wednesday’s event.

The former Massachusetts governor wrote an opinion piece on foreign policy Sunday in the Wall Street Journal, accusing the Obama administration of minimizing the seriousness of the attack on the U.S. Consulate in Libya and the other threats facing the U.S. in the region.

Romney writes, quote, ‘‘our values have been misapplied — and misunderstood’’ by Obama. He also says Obama has distanced the U.S. from Israel.

In a statement released late Sunday Philips Electronics said they were pulling out as sponsors of the presidential debates.

‘‘While the Commission on Presidential Debates is a nonpartisan organization, their work may appear to support bi-partisan politics,’’ Mark A. Stephenson, head of corporate communications for Philips North America, said in the statement. ‘‘We respect all points of view and, as a result, want to ensure that Philips doesn’t provide even the slightest appearance of supporting partisan politics.’’

At issue is the commission’s decision to limit the debates to the two main party candidates.

The Commission on Presidential Debates could not be reached for comment Sunday.