HARRISBURG -- If John McCain is to win the presidency Nov. 4, he must carry Pennsylvania and Ohio, said former Gov. Tom Ridge, a close friend and political ally of the Republican candidate.

"Candidly, unless we win Pennsylvania, I don't think he's elected president," the Republican former governor said at a breakfast with Harrisburg reporters yesterday. "We have to win Pennsylvania."

He later added Ohio to the "must win" list.

Mr. Ridge acknowledged that Mr. McCain was trailing in most polls of Pennsylvania voters, but said he doubted that Democratic candidate Barack Obama was leading by double digits, as some polls have claimed. Mr. Ridge put the Obama lead in the range of 2 to "5 or 6" percentage points.

"We know we are in a tough fight, but I don't see a double-digit [Obama] lead," he said. "I'm not buying that."

And people have mistakenly written off Mr. McCain too soon in the past, only to see him bounce back, Mr. Ridge added, and he predicted that the Arizona senator would do so again Nov. 4.

"We may be down in the polls, but our spirits are good, and the opportunity to prevail in Pennsylvania is good," he said. Research by the McCain camp is showing that "some undecided voters and independents are starting to break our way."

The Republican nominee will do well in Western Pennsylvania, "where there are a lot of independent-thinking and -voting Democrats," Mr. Ridge said. Mr. McCain also will do well in the "T," the nickname for the state's north-south midsection and broader northern areas that are mostly small towns and rural stretches.

Mr. Ridge said the Scranton area has a lot of "Reagan Democrats," people registered as Democrats who have conservative social and fiscal values espoused by Republican former President Ronald Reagan.

Heavily Democratic Pittsburgh and Philadelphia will side with Mr. Obama, the former governor said. But the four large, suburban counties surrounding Philadelphia will be, perhaps, the key battleground. Traditionally Republicans did well in Bucks, Montgomery, Chester and Delaware counties, but those areas have been trending more Democratic in recent years, so that is a major challenge for Mr. McCain, Mr. Ridge said.

This week, Mr. McCain visited three areas of Pennsylvania, including Moon and Harrisburg, and will appear Tuesday with his running mate, Alaska Gov. Sarah Palin, at Hershey's Giant Center, a hockey arena.

Gov. Ed Rendell has written to the Obama headquarters in Chicago, urging campaign officials to bring back the Democratic nominee several more times before Nov. 4, because Mr. McCain and Ms. Palin have lately spent a lot of time in the state.

In a conference call with reporters yesterday, Obama campaign manager David Plouffe said he was well aware that Mr. McCain is making "a strong effort" in Pennsylvania, and insisted that Mr. Obama wasn't taking the state for granted, even though he is ahead in statewide polls. A GOP presidential candidate hasn't won in Pennsylvania since 1988.

For Mr. McCain to win Pennsylvania's 21 electoral votes, he would need to win 95 percent of all Republican voters, 60 percent of independents and 15 percent of Democrats, Mr. Plouffe said.

He doubted the possibility of that. "It's hard to see him getting 15 percent of Democrats, and we are also strong with independents in Pennsylvania," he said. "We will continue to campaign hard in Pennsylvania. We have a 1.2 million-voter registration advantage there."