Sen. John McCain - remember him?

The Arizona Republican surely hopes so.

But with Barack Obama and Hillary Rodham Clinton set to hog the headlines for weeks with their primary slugfest in Pennsylvania, what's a presumptive GOP nominee to do?

McCain responded yesterday by packing a Delaware County ballroom with supporters for a "town hall" session, and vowing to do what no Republican presidential candidate has for 20 years: carry Pennsylvania.

"I do recognize that Pennsylvania will be a key battleground state," McCain told reporters after his appearance in the ballroom of the Springfield Country Club. He said he planned a series of such meetings across the state.

"I also understand, when you have a very heated race on the other side between Sen. Obama and Sen. Clinton, that it's going to get a lot of attention," McCain said. "So I'm going to have to work all the harder."

Philadelphia's suburbs will be a key front on that battleground. The suburban vote, once considered a Republican lock, has increasingly gone Democratic in national and statewide contests.

And that isn't the only losing streak McCain faces. He joked that he was among a series of presidential candiates from Arizona - e.g., Barry Goldwater, Morris Udall, Bruce Babbitt - who had run and lost.

"Arizona may be the only state in America where mothers don't tell their children that someday they can grow up to be president," he quipped.

In an opening address and a give-and-take session with his audience, McCain stuck to the script that has worked for him: Stay the course in Iraq, rein in spending, retrain unemployed workers, make the Bush tax cuts permanent, reduce dependency on foreign oil, seal the borders.

He focused in particular on a longtime peeve: pork-barrel spending by lawmakers through money earmarked for projects on their home turf. McCain was smarting from the Senate's rejection on Thursday of an election-year moratorium on earmarks.

Only 29 Senators supported the measure - McCain, Obama and Clinton among them. Yesterday, McCain challenged his Democratic opponents - both of whom have received earmarks in the past - to give back whatever remains unspent.

McCain said $36 billion in earmarks had been attached to domestic spending bills in the past two years. "As president, we will veto those bills," he said.

McCain hopes to benefit in Pennsylvania from the support of former Gov. Tom Ridge and other prominent Republicans. But when asked whether Ridge - or former Secretary of State Colin Powell - would be considered for vice president, he refused to tip his hand.

Calling Ridge a "great, dear friend," McCain said his campaign had "not even begun the process" of checking into potential running mates.

Questioned about the gun violence that has plagued the region, McCain stood firmly behind the right to bear arms.

"I'm very aware . . . of the number of killings and murders that are taking place in the Philadelphia area. It's tragic and it's terrible," McCain said.

"I do believe in protecting the constitutional right ensured by the Second Amendment," he added as the room erupted in cheers. He said he would increase support to police agencies and backed "very strong mandatory sentences for crimes that are committed with a weapon."

McCain received a standing ovation when it was announced that yesterday was the 35th anniversary of his release from captivity as a prisoner of war in Vietnam.

Asked to reflect on that, McCain said, "Certainly, the day I was released, I didn't anticipate I'd be standing here before you."

His Democratic opponents, meanwhile, announced that they had agreed to a nationally televised debate April 16 at the National Constitution Center.

Obama has no scheduled appearances this weekend in Pennsylvania. Clinton, who campaigned yesterday in Pittsburgh, is scheduled to march today in the Iron City's St. Patrick's Day parade before traveling to Scranton for another Irish-theme celebration.

Contact staff writer Larry King at 215-345-0446 or lking@phillynews.com.