Mitt Romney and running mate Paul Ryan look to shrug off the latest in a series of unwanted distractions when they face Ohio voters as the Republican presidential ticket for the first time.
The two men are appearing at a Columbus-area rally Saturday morning, less than 24 hours after Romney raised the discredited rumor that President Barack Obama wasn't born in the United States. The comment, and his efforts to explain it, overshadowed Romney's economic message as he campaigned near his Michigan birthplace on Friday.
At the same time, Obama is launching a new Medicare offensive using his radio and Internet address and a new campaign ad to help highlight Romney's plans for the health care program for seniors.
The president does not mention his Republican challenger in his weekly radio address, but said that the Medicare program is about keeping promises to millions of seniors who have put in a lifetime of hard work.
Obama's new 30-second television ad says Romney "would break that promise" and replace the current Medicare system with a voucher program that wouldn't keep up with costs.
"Insurance companies could just keep raising rates," the new ad says.
Romney's Ohio rally is expected to be his final public appearance of the weekend ahead of the Republican National Convention in Tampa, Fla., where the former Massachusetts governor will formally accept the presidential nomination.
While GOP officials suggest they have momentum on their side heading into the crucial period, Romney and his party have faced tough questions in recent weeks on Medicare and abortion.
Now his joking reference to the president's birth certificate links him to the so-called birther movement and a wing of his party — a combined 25 percent in an April Pew Research Center poll — that says it either isn't sure or doesn't believe Obama was born in the United States.
Earlier in the week, Romney caused another stir by declaring that big business was "doing fine" in the current struggling economy in part because companies get advantages from offshore tax havens.
Still, polls suggest that the presidential contest is essentially a tossup as Obama struggles under the weight of the nation's weak economy.
The president's re-election campaign has pushed voter attention away from the economy in recent weeks, particularly after Romney's selection of his running mate, Ryan, the architect of a controversial budget plan that would transform Medicare into a voucher-like system for future retirees.
Democrats have also seized on Missouri Senate candidate Rep. Todd Akin's recent suggestion that women's bodies can prevent pregnancy in cases of "legitimate rape."
The congressman announced Friday that he would not leave his Senate contest despite overwhelming pressure from Romney and top Republican officials.
Romney made his birth certificate remark at a large outdoor rally in Michigan, where he grew up and where his father, George, served as governor. He told supporters that he and his wife, Ann, had been born at nearby hospitals.
"No one's ever asked to see my birth certificate. They know that this is the place that we were born and raised," Romney said.
The crowd of more than 7,000 responded with hearty laughter.
Obama campaign spokesman Ben LaBolt swiftly denounced the remark, saying Romney "embraced the most strident voices in his party instead of standing up to them."
Romney was asked about his remark in a CBS interview later in the day.
"No, no, not a swipe," Romney said. "I've said throughout the campaign and before, there's no question about where he was born. He was born in the U.S. This was fun about us and coming home. And humor, you know — we've got to have a little humor in a campaign."
The authenticity of Obama's birth certificate has been questioned by some Republican critics who insist Obama is not a "natural-born citizen" as required by the Constitution. Obama released a long-form version of his birth certificate last year as proof that he was born in Hawaii in 1961.
But conservative questions have lingered. And Romney has declined to condemn such questions, particularly from prominent donor Donald Trump.
The Obama campaign released a web video Friday night featuring Romney's remark and declaring that, "America doesn't need a birther-in-chief." Democrats intend to keep the pressure on as the Republican convention gets under way.
Obama was spending the weekend at Camp David, the presidential retreat in Maryland, as Republicans began gathering in Tampa for their convention. But Democrats were planning to counter Romney's message throughout the week.
Reaching out to young voters, a key component of his 2008 election, Obama was making stops in the college towns of Ames, Iowa, Fort Collins, Colo., and Charlottesville, Va., on Tuesday and Wednesday.
Vice President Joe Biden canceled plans to give a speech in Tampa on Monday, a short distance from the convention site, to help ensure emergency officials can focus on Tropical Storm Isaac. But he is expected to travel on Tuesday to Orlando and St. Augustine, Fla.
Shortly after Ryan gives his convention address on Wednesday night, first lady Michelle Obama is set to appear on CBS' "Late Show With David Letterman," offering a counter to the Republican message. The high-profile events are paired with a number of smaller gatherings around the country by Democrats aiming to attract female voters and a bus tour with party activists in Ohio, Pennsylvania and Wisconsin.
Obama campaign deputy campaign manager Stephanie Cutter said the president's team was "not going to cede four days of this campaign just because of a party convention."