HERSHEY, Pa. — Doubts about John McCain's chances for the presidency grew louder among fellow Republicans yesterday as a White House race largely focused on Florida, Ohio and Pennsylvania entered its final week.

Even two Republicans once on McCain's short list for vice president sounded skeptical. In a fundraising e-mail on behalf of Senate Minority Leader Mitch McConnell of Kentucky, Mitt Romney referred to "the very real possibility of an Obama presidency." In the Midwest, Gov. Tim Pawlenty gave a dour assessment of McCain's chances in his state, saying Barack Obama "has a pretty good advantage in Minnesota right now."

Nationally, a poll by the Pew Research Center found Obama with a 16-point lead among registered voters. The survey said Obama had 52 percent and McCain 36 percent, with independent voters supporting the Democrat by a 48-31 margin.

The Nielsen media company reported that both are focusing about three-fourths of their advertising in Florida, Ohio and Pennsylvania. Obama, who had been spending four times as much as McCain on advertising, is now airing only twice as many ads as his rival, the ratings company said.

Those three states are battlegrounds, offering a combined 68 electoral votes on Election Day.

The candidates kicked off their final week of campaigning in the southeastern corner of Pennsylvania, which hasn't supported a Republican presidential candidate in 20 years and where Obama is ahead in the polls. McCain is working for an upset and has Pennsylvania as the linchpin to his victory strategy.

"I'm not afraid of the fight, I'm ready for it," McCain told noisy supporters at a rally in Hershey, a Republican region and home of the world's largest chocolate factory.

Obama's advisers say they are confident of victory in the state. Still, they sent him to rally supporters in Pittsburgh on Monday night and to the battleground Philadelphia suburbs yesterday. About 9,000 people stood in the mud and a steady, cold rain at Widener University to hear him.

"I just want all of you to know that if we see this kind of dedication on Election Day, there is no way that we're not going to bring change to America," said Obama, uncharacteristically attired in jeans, sneakers and a raincoat. McCain canceled a second event in Quakertown because of the dismal weather.

McCain appeared with running mate Sarah Palin, who planned to stay in the state for rallies in Shippensburg and State College. "Pennsylvania, it's going to be a hard-fought contest here," she said. "It's going to come down to the wire here."

If McCain doesn't win the state's 21 electoral votes, it's hard to see how he can win the presidency since Obama is expected to pick up several states that helped re-elect President Bush.