Republican Arizona Sen. John McCain will cross Pennsylvania with the sun today, starting with a morning rally in Bucks County, moving on to Harrisburg and making his day's final stop in Moon.

The destinations are the latest evidence of his concentration on a state that could provide a counterbalance to potential losses for the McCain ticket in traditionally Republican states being aggressively courted by his well-funded presidential opponent, Democratic Illinois Sen. Barack Obama.

That strategy, of course, assumes that Mr. McCain can win Pennsylvania, a prospect that flies in the face of recent polling showing the Democrat with a larger lead here than in any other battleground state.

"We love Pennsylvania," McCain campaign manager Rick Davis said in a conference call yesterday, as he dismissed poll-driven suggestions that his boss might make better use of his time in a state where the race appears tighter. "Pennsylvania is our kind of place; we anticipate winning Pennsylvania. We don't believe any of the naysayers who say Pennsylvania is out of reach."

While Mr. Obama is outspending the Republican by a significant margin in Pennsylvania television advertising, Mr. McCain has spent more time in the state than his opponent. In the last week, he made appearances in Montgomery and Chester counties, which, like his Bucks County stop today, lies within the vote-laden belt of suburbs surrounding Philadelphia.

Adding to Mr. McCain's challenge is the fact that Bucks County, like Montgomery County, has produced a Democratic voter-registration edge for the first time in a generation this year, largely because of the Obama campaign's registration efforts. Dauphin County, where the Harrisburg rally will take place, also switched from a GOP to a Democratic registration plurality in the last year.

Alaska Gov. Sarah Palin, Mr. McCain's running mate, has made major recent appearances in Johnstown and Scranton. And Cindy McCain, who is usually at her husband's side, made a string of solo appearances over the weekend in eastern and central Pennsylvania.

Mr. Obama addressed a series of rallies in Philadelphia 10 days ago. His campaign has announced no plans for him to return to the state.

Instead, the Democrat has been appearing in a series of states carried four years ago by President Bush, in an aggressive effort to widen the map of competitive states. With the exception of Pennsylvania, Mr. McCain's itinerary has also concentrated on Bush states, a defensive strategy from the GOP point of view.

Mr. McCain is appearing late today at Sewall Center on the Robert Morris University campus in Moon. The public may obtain event tickets at regional Republican Party and McCain campaign offices.