In the final stretch of a presidential campaign, the schedules of the candidates speak volumes about what's really going on, even more than the polls.

For the last 10 days, Democrat Barack Obama has been on the offense, campaigning exclusively in states won by President Bush four years ago. He even felt confident enough last week to visit Indiana, which hasn't gone Democratic since 1964.

Republican John McCain has been working those same red states, playing defense; his predicament is such that on Tuesday, he's scheduled to go to North Carolina, even though it has voted Republican the last seven times.

McCain's only blue-state destination has been Pennsylvania, which he has visited repeatedly, searching for a solution to his daunting Electoral College problem.

At this stage, nine days before Election Day, Pennsylvania might be the only state that both sides believe they must win. And it is getting the attention that comes with such status.

Tomorrow evening, McCain will be in Pottsville while Obama stumps in Pittsburgh. Tuesday morning, McCain will be in Hershey, Obama at Widener University in Chester. Republican vice-presidential candidate Sarah Palin is in the state practically full time.

Beyond Pennsylvania, the reality of the race is that Obama has multiple paths to reach the needed 270 electoral votes, and McCain's options are few.

State polls suggest that if everything breaks right for Obama, he might approach the 379 electoral votes that Bill Clinton amassed in 1996 when he won reelection against Bob Dole.

In part because of his financial advantage, Obama is competitive in places that were off-limits to Democrats for years.

"Strategically, we tried to have as wide a map as possible," Obama campaign manager David Plouffe said Friday, ". . . and we think we've been able to create that dynamic."

The tilt of the playing field helps explain McCain's focus on Pennsylvania despite trailing in state polls by about 10 points. He has no other choice.

The reason is that Obama is ahead in all of the states the Democrats carried in 2004, including Pennsylvania, and in some states won by the GOP.

Consider this winning McCain scenario, improbable as it seems at the moment.

Assume he loses the four red states where the Obama campaign feels it's strongest: Colorado, Iowa, New Mexico and Virginia. Assume, too, that McCain wins every other contested red state - Missouri, Florida, Ohio, Nevada, Indiana and North Carolina - even though he trails in most of them now.

If all of that happened, McCain would eke out a 273-265 victory by winning Pennsylvania.

"We don't believe any of the naysayers who believe Pennsylvania is out of reach," McCain campaign manager Rick Davis said last week.

From the beginning, Davis and company understood that Obama was likely to win some traditionally Republican states, and that they'd have to make inroads in the Democratic base.

Initially, Pennsylvania and Michigan, with their older populations and socially conservative Democrats, looked like the best prospects.

But McCain abandoned Michigan as hopeless weeks ago. That forced him to keep fighting in Pennsylvania, hoping to take advantage of the doubts about Obama that voters, mostly outside the Philadelphia area, demonstrated during his primary defeat to Hillary Rodham Clinton.

"We need to carry Pennsylvania to win this thing," former Gov. Tom Ridge acknowledged a few days ago, later adding: "You don't want to write John McCain off, ever. . . . If John McCain has a Webster's dictionary, there are a couple of words that are not in it:

surrender, quit

or

give up

."

State Democratic leaders said they believed McCain's Pennsylvania fixation made a certain amount of sense.

No Democratic presidential candidate since Lyndon Johnson has received more than 51 percent of the vote in the state, even though the party has carried it the last four times. So it's reasonable to expect a close outcome.

"We're going to make a huge effort in Pennsylvania," said Plouffe. "As unlikely as it is for them [Republicans] to succeed, we've got to take that seriously, and we will."

As Gov. Rendell has noted, the Electoral College formula for winning a presidential election has been in place for years: The party that takes at least two of the three biggest swing states - Pennsylvania, Florida and Ohio - takes the White House.

That formula has proved valid in the last 11 elections, with Ohio voting for the winner every time. But even that rule might not hold this time.

With his strength in the West and in Virginia, Obama might be in position to win while losing Ohio and Florida - although he could win either one - as long as he hangs on in Pennsylvania.

Obama chief strategist David Axelrod said months ago that his goal was to go into election night not depending on Florida, which decided the outcome in 2000, or Ohio, which was pivotal in 2004.

McCain pushes on, attempting to win as many of the red states as possible and make his mark in Pennsylvania.

He is campaigning largely on the basis of three points: his criticism of Obama's tax plan, which he describes as income redistribution; his foreign-policy experience, which he compares to that of his "untested" opponent; and the specter of the Democrats having "total control" of the presidency and Congress.

Obama, after visiting his gravely ill grandmother in Hawaii, returned to the campaign trail in Nevada yesterday, belittling McCain's recent attempts to separate himself from President Bush and promising a tax cut for 95 percent of wage-earners.

In a campaign in which national security has taken a backseat, an international incident in the closing days might alter the race in McCain's favor. But the impact of such a crisis might be muted by the fact that the election is happening already.

Analysts expect a record 30 percent of the popular vote to be cast before Nov. 4 via absentee ballot or early voting in the 31 states that allow it. And indications are that Democratic turnout is running high.

Contact senior writer Larry Eichel at 215-854-2415 or leichel@phillynews.com.

Inquirer staff writer Mario F. Cattabiani contributed to this article.