RALEIGH, N.C. (AP) — Differences between Mitt Romney and Paul Ryan's positions — this time on hot-button social issues — were on display Wednesday as the GOP ticket found itself dragged into a debate over abortion. The vice presidential candidate emphasized anew that Romney is the nominee, brushing aside differences in their records. "I'm proud of my pro-life record. And I stand by my pro-life record in Congress. It's something I'm proud of. But Mitt Romney is the top of the ticket and Mitt Romney will be president and he will set the policy of the Romney administration," Ryan told a Pennsylvania TV station. Romney does not oppose abortion in cases of rape and incest or if it will save the mother's life, while Ryan does oppose abortion in cases of rape and incest. Since choosing Ryan as his running mate, Romney has been dogged by questions about how his own views differ from the Wisconsin congressman's. Ryan is the architect of a controversial budget blueprint that would dramatically change Medicare, and after his selection Democrats immediately began trying to tie Romney to his new No. 2's plan. The likely Republican nominee has said his plan is different, but largely refused to outline specifics of the differences. Instead, he's emphasizing what he calls shared principles and insisting that Ryan joined the Romney ticket, and not the other way around. The focus on abortion comes in the wake of comments from Missouri Senate candidate Todd Akin, who is challenging Democratic Sen. Claire McCaskill. Asked in an interview aired Sunday if abortion should be legal in cases of rape, Akin said: "If it's a legitimate rape, the female body has ways to try to shut that whole thing down." Ryan on Wednesday defended a bill he cosponsored in the House to permanently ban federal funding for abortion except in cases of incest and "forcible" rape. That language, which was eventually changed, would have narrowed the exception for rape victims. Akin and 225 other members of the House, including 11 Democrats, also cosponsored the bill. Democrats have seized on the bill and accused Ryan of trying to "redefine rape and remove protections for rape victims." "As a Republican leader in the House, Paul Ryan worked with Todd Akin to try to narrow the definition of rape and outlaw abortion even for rape victims," Obama campaign spokeswoman Lis Smith said in a statement. Akin has refused to heed calls to step down — including one from Romney — and now would need a court order to leave the race. He has until Sept. 25 to do so; after that point, he would have no way to remove his name from the ballot. Ryan, a colleague of Akin's in the House, called the Missouri congressman to urge him to bow out of the Senate race. Ryan said Wednesday he doesn't have any plans to speak to him about it now that Akin is staying in. "He's going to run his campaign and we're going to run ours," Ryan said of Akin. The questions about abortion were overshadowing the GOP ticket's campaign events in Iowa, Virginia and North Carolina Wednesday, as they were seeking to attack President Barack Obama's stands on Medicare and again minimize the differences between Romney and Ryan on that subject. That comes in a new TV advertisement linking Obama's divisive health care overhaul to cuts in Medicare. The ad, titled "Nothing's Free," asserts that Obama raided $716 billion from Medicare in order to pay for his health care law. It's the first ad Romney's campaign has run focusing on health care since the Supreme Court upheld Obama's federal mandate in June Romney has promised to roll back the Medicare spending cuts approved under Obama, while Ryan kept the cuts in his budget proposals. The campaign did not say where the health care ad would run. Romney was flying Wednesday morning from Texas, where he held campaign fundraisers Tuesday, to Iowa. During remarks in a key Midwestern state, he planned to focus on the increases in the nation's debt during Obama's term. Ryan, less than two weeks into his new role as GOP running mate, was campaigning in Virginia and North Carolina and focusing Wednesday on a tax overhaul. The GOP campaign says Obama's calls for letting George W. Bush-era tax cuts on people earning more than $200,000 a year expire at the end of the year would hurt small businesses because many file as individuals. Obama, meanwhile, readied for a second straight day of criticism on the GOP ticket's proposals on education, an issue that resonates with middle-class voters. Obama was campaigning Wednesday in Nevada, one of the states hit hardest by the nation's economic slowdown. The president planned to meet with teachers at a Las Vegas high school and promote his administration's plans to make higher education more affordable before speaking at a larger event at the school. Campaigning in Ohio Tuesday, Obama accused Romney of being oblivious to the burdens of paying for college. The president's campaign sees education as another avenue for linking Romney to Ryan's budget, which calls for $115 billion in cuts to the Education Department. In a new ad released Wednesday, the Obama campaign suggests Ryan's education cuts would lead to larger class sizes. A couple featured in the ad bemoans the prospect of increased class size and says Romney "cannot relate" to their desire to have the best public education system for their children. The ad is running in Virginia and Ohio.