Ludwig, a registered Republican and mother of two teenagers, voted for Obama in 2008 when he won Pennsylvania by more than 10 percentage points. But now she has misgivings.

“I really expected him to make changes,” she said as she ate lunch last week with her husband, Jim, at an outlet mall in Gettysburg. “But he didn’t. He disappointed me.”

Such sentiments, among other signs, are prompting Romney and his allies to pour money into this large state even though Republican presidential nominees have lost here five straight times despite substantial efforts. Some independent analysts say the same result is likely this year, even if few expect Obama to repeat his double-digit victory.

But if Republicans can make Obama sweat and scrape for Pennsylvania, it will consume resources he otherwise could use in crucial states such as Florida and Ohio. It also might demoralize Democrats and assure Romney’s fans everywhere that the former Massachusetts governor has a solid chance to win the White House.

Pennsylvania “is still an uphill climb for Romney,” but “conditions are nowhere near as advantageous for the president as they were in ’08,” says Christopher Borick, a pollster and political scientist at Muhlenberg College in Allentown, Pa. From Obama’s standpoint, Borick said, “there are a lot of little nagging issues.”

Several small factors conceivably could put Romney within striking distance.

Among them: A new Republican-written state law that requires voters to show a photo identification card could suppress turnout among minorities. Some Catholic voters are angry at the Obama administration for initially requiring Catholic-affiliated employers to cover contraceptive products in their insurance policies. And Romney’s image as a moderate Republican who focuses more on economic matters than social issues could play well with swing voters in the Philadelphia suburbs.

At same time, however, Pennsylvania’s unemployment rate is somewhat below the national average. And despite a disastrous 2010 midterm election, in which Republicans gained full control of the state Legislature and won the governor’s race, Democrats retain a big advantage in voter registration.

Obama campaign manager Jim Messina says Democrats will fight hard to win Pennsylvania again.

“We have a huge ground operation,” Messina said, including two dozen offices in the state, far more than Romney has.

Women in the Philadelphia suburbs are a crucial target, Messina said, and he thinks they will be turned off by comments from top Republicans regarding reproductive rights, equal pay and other issues.

David James, a top Romney adviser in Pennsylvania, agrees that Philadelphia suburban women are a vital group. But he says Messina is mistaken about the extent of the gender gap, in which Democrats typically have an edge with women and Republicans hold an edge among men. Suburban women’s top concern, James said, “is the economic security of their families,” and Romney’s promise to create jobs and economic growth will appeal to them.

Romney will compete heavily in Pennsylvania, James said. The campaign started slowly because of the state’s late primary, he said, but “June is our big growth month.”

At least $6.8 million has been spent on presidential campaign TV ads in Pennsylvania since early May. Obama’s campaign has spent $2.8 million, while a Democratic super PAC, Priorities USA, has devoted $1.2 million. Romney’s campaign is not on the air in the state, but a Republican super PAC, Crossroads GPS, has spent about $2.8 million.

The most recent independent poll in Pennsylvania, by Quinnipiac University, showed Obama leading Romney 47 percent to 39 percent.

But the month-old survey was taken before May’s dismal employment numbers were released. And Republicans found some comfort in the president remaining below 50 percent statewide and trailing Romney in the Scranton area, a region Obama carried easily four years ago.

To combat the new state law, Obama volunteers and paid staffers are trying to find potential voters who lack photo I.D. cards, and then helping them qualify to vote. The new state law requires I.D. cards to include an expiration date, something that many college student cards lack.

At Temple University in Philadelphia, voter registration forms will go out with the roughly 5,000 freshman orientation packets for the first time this fall. Students say their I.D. cards are being revamped to include expiration dates.

Republicans say voter I.D. laws are needed to avert voter fraud, an alleged problem for which there’s scant evidence. Democrats say the laws are designed to depress turnout by low-income people and minorities, who tend to vote Democratic.

Strategists in both parties say the prime target in Pennsylvania is swing voters in the heavily populated four-county Philadelphia suburbs. Republicans there tend to be moderate, more focused on economic matters than religious issues.

Andrew Reilly, chairman of the Delaware County GOP, acknowledged the Democrats’ statewide voter registration advantage. But he said Romney is the first Republican presidential candidate in 20 years who fits well with the area’s GOP electorate.

“Pennsylvania is a challenge,” Reilly said. “I think Romney’s got a shot.”

Messina, Obama’s national campaign manager, said issues that will make Romney less appealing in Pennsylvania, as in several other manufacturing states, include his opposition to Obama’s auto industry rescue and his support of tax cuts for millionaires. “We’re going to win Pennsylvania with a great campaign,” Messina said.

It may take a good campaign to win back Candi Ludwig, who said she hasn’t committed to Romney despite her disappointment in Obama.

James, the Romney adviser, says a smart, energetic campaign can lure such voters to the GOP column. “2012 is not 2008,” James said. “We believe we can win Pennsylvania. And if we win Pennsylvania, Mitt Romney will be president.”

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Associated Press writer Marc Levy contributed to this report.