ERIE, Pa. -- The Republican campaign bus roared into the party headquarters parking lot in the northwestern Pennsylvania town of Erie on a chilly afternoon for a rally that had all the trappings of a close contest.

Hundreds of people wearing Romney-Ryan buttons and hats, plus one man carrying a “NObama” sign, crammed inside the headquarters and cheered loudly as party officials blasted President Barack Obama. Volunteers manned telephone banks imploring people to vote.

Why the Republican hubbub in a state that’s voted Democratic in presidential elections for two decades? They think it might be in play.

Obama leads Mitt Romney in Pennsylvania polls by an average of 4.8 percentage points, according to the nonpartisan website RealClearPolitics.com. Obama led by as much as 12 points earlier this year. And he led by 10.8 points at this stage four years ago.

“Mr. Obama thinks he has Pennsylvania already,” said Dr. Winston Chu, the Erie County Republican Party vice chair. “And Mr. Romney is just finding out that he has a good chance here.”

Republicans are pushing for a late appearance by Romney or running mate Rep. Paul Ryan of Wisconsin, an unexpected personal play for the state’s 20 electoral votes, which they think could make Romney the first Republican candidate to carry the state since George H.W. Bush in 1988.

“We’ve certainly suggested that we are in play,” said Republican former Pennsylvania Gov. Tom Ridge, who traveled in the Romney bus through parts of the state Friday with Republican National Committee Chair Reince Priebus and former Pittsburgh Steelers wide receiver Lynn Swann, who unsuccessfully ran for governor in 2006.

“They’re talking about his schedule. . . . I can’t say yay or nay. One of the things most people don’t understand is they’ve invested quite a bit of money quietly in Pennsylvania. We have already knocked on more doors and made more phone calls and have more people on phone banks than we did in ’04 and ’08 together. . . . Obviously, I’d like to see my guy pop down here but there are 270 (electoral) votes, and we don’t have that many. But the dynamics of this race are changing.”

Democrats dismiss the notion of a Romney upset as Republican wishful thinking. They note that Obama soundly defeated Republican presidential candidate John McCain by 10 points in 2008, that Romney hasn’t aggressively campaigned in the suburbs of Philadelphia and Pittsburgh – areas he needs to win to counter Democratic urban votes – and that Romney’s campaign and supporting groups have spent a pittance on advertising in the state.

Still, the Obama campaign said Monday that it would start airing ads in the state to counter those from a pro-Romney group. "We’re not going to take anything for granted," campaign manager Jim Messina said. And the campaign is dispatching Vice President Joe Biden to rally supporters later this week.

One Pennsylvania analyst is skeptical about the possibility of a Romney win.

“He has to win the Philly suburbs and the Lehigh Valley, hope turnout in Philly is low and do well with Roman Catholics,” said G. Terry Madonna, the director of the Center for Politics and Public Affairs at Pennsylvania’s Franklin and Marshall College. “He’s still not doing well enough in the Philly and Pittsburgh suburbs. It’s close enough that you can’t say ‘never.’ But four points with little more than a week out is hard to make up.”