WASHINGTON -- The dust-up over Sen. Barack Obama's remarks about rural America is forcing both Democratic candidates to talk about guns, abortion and family values -- issues that don't win them many votes among the social conservatives they are trying hard to court in the Rust Belt, South and West.

Republicans saw themselves as the beneficiary as the furor continued to grow. Republican candidate Sen. John McCain said Monday that his campaign would use the remarks to paint the Illinois senator as a liberal elitist, much the way the Republican Party portrayed former Vice President Al Gore and Sen. John Kerry as out of touch in the past two elections.

Sen. Obama said Monday that he had made a mistake when he told a private San Francisco fund-raiser April 6 that after years of broken promises, small-town Pennsylvania voters had grown bitter, and "they cling to guns or religion or antipathy to people who aren't like them...as a way to explain their frustrations."

WSJ's Jake Schlesinger analyzes the aftermath of Sen. Barack Obama's controversial remarks about small-town Pennsylvania voters and says the state's primary will determine how much damage his campaign has suffered as a result. (April 14)

But he used the controversy to renew his case that his rival for the Democratic nomination, Sen. Hillary Clinton, would say anything to win votes and that voters would see past his opponents' attempts to use the comment to paint him as a "card-carrying liberal."

"Not just Democrats but also independents and Republicans are recognizing that how we function politically is not working," he told hundreds of journalists at a luncheon in Washington. "That it's become a sport. It's become a game, and we never get to the point of governing."

Tuesday, the Clinton campaign released Monday night a new advertisement in some parts of Pennsylvania focusing on Sen. Obama's gaffe. "I'm not clinging to my faith out of frustration and bitterness. I find that my faith is very uplifting," one female voter says in the ad.

Both Democratic candidates laid into each other at a forum on manufacturing in Pittsburgh in advance of Pennsylvania's April 22 primary. In a sign that the infighting is becoming irksome, some audience members booed when Sen. Clinton brought up Sen. Obama's remarks. "I know that many of you, like me, were disappointed by recent remarks he made," Sen. Clinton said, to hissing from the crowd. "No, no!" shouted some audience members. Sen. Obama earlier had criticized Sen. Clinton at the forum.

Sen. McCain described Sen. Obama's remarks as "elitist" and said they show "a fundamental misunderstanding of the American people." And his campaign was quick to paint a contrast in a fund-raising appeal to supporters. "If Barack Obama is the Democrat nominee in the general election, the American people will have a clear choice between two different visions -- Sen. Obama's liberal, elitist philosophy and John McCain's faith in the small-town values that continue to make America great," campaign manager Rick Davis said in an email.

Sen. Obama has tried to reframe the conversation by defending his claim that Americans are bitter and frustrated, but Sen. Clinton has used his assertion that Americans "cling to guns or religion" to trumpet her own credentials as a friend of hunters and sportsmen.

That strategy, too, has risks, because Sen. Clinton strongly championed tougher gun measures during the Clinton administration and when she ran for her Senate seat in 2000, and even now is proposing a crackdown. In West Philadelphia last week, Sen. Clinton laid out a $4 billion-a-year plan to cut crime and murders in metropolitan areas, in part by renewing the Assault Weapons Ban and enhancing tracking of illegal guns.

She cited the drop in murders by illegal firearms during her husband's administration. "We've got to get back to doing what works," she said.

Speaking to Second Amendment supporters Saturday in Valparaiso, Ind., Sen. Clinton didn't mention the crime bill. Instead, she talked about her positive experience with firearms. "As I told you, my dad taught me how to shoot behind our cottage," she said. "I have gone hunting. I am not a hunter, but I have gone hunting."

Sen. Clinton says she has hunted ducks, but pressed by reporters Sunday to name the last time she used a gun, she said that the question was "not relevant."

Her gun-rights credentials set off a firestorm from Sen. Obama, who mocked her Sunday for "talking like she's Annie Oakley," the frontier sharpshooter, and acting like "she's out in the duck blind every Sunday."

Sen. Obama's comments about guns could complicate his much-heralded promise to aggressively compete in traditional Republican states such as Virginia this fall.

Sens. Obama and Clinton differ little on gun control and abortion, and seldom speak about the issues on the stump unless asked. Each stresses the need to reduce the number of abortions, and both are quick to emphasize their view that the Second Amendment is an individual right, a view that isn't widely held by gun-control supporters. The Supreme Court will rule later this year on the constitutionality of the Washington, D.C., ban on handgun use.

Some Democrats believe Mr. Gore's support for gun control cost him states -- such as West Virginia -- that would have delivered him the 2000 election, and Sen. Kerry largely shied away from similar support in 2004.

It isn't clear how successfully Sen. McCain could exploit the gun issue, in part because he has been vilified by the National Rifle Association for his role in pushing campaign-finance-reform legislation and for supporting tighter rules on gun shows.

In a sign that the NRA may put aside its divisions to defeat the Democratic nominee this fall, the group's executive vice president, Wayne LaPierre, said that despite some "bumps in the road with McCain...when you start putting the records side by side there's a big, big difference."

Sen. Obama Monday pointed to his home state of Illinois, where sportsmen in the south "view gun ownership as deeply held traditions," while gun violence has claimed 22 Chicago public-school children this year. "We keep talking past each other on that issue," he said.

The candidates likely will be forced to address gun violence at the presidential debate in Philadelphia on Wednesday, the one-year anniversary of the Virginia Tech shootings, in which 32 were killed.

Write to Nick Timiraos at nick.timiraos@wsj.com and Amy Chozick at amy.chozick@wsj.com