"The Mac is back," a smiling Sen. John McCain told a hangar full of cheering supporters at the Pittsburgh International Airport yesterday.

Back again, he might have said. The Republican nominee has returned to Pennsylvania again and again in recent months seeking its 21 electoral votes as a vital building block in his long-shot bid to put together an Electoral College majority. His rally yesterday was one stop in his final, frenetic charge across seven states in his upset quest for the White House.

Mr. McCain began his day in Tampa, Fla., courting votes in another pivotal state at the close of the longest, most expensive presidential race in the nation's history. His opponent, Sen. Barack Obama also began his day in Florida, where polls and early voting statistics suggested that he was poised to become the first African-American president in U.S. history.

Most final tracking polls put his standing at above 50 percent, a threshold no Democratic presidential candidate has reached in a generation.

After two presidential elections decided by razor-thin margins, he campaigned in states whose addition to the Democratic column could decide the election by a landslide. Mr. McCain was grasping for a victory that, by however slim a margin, would be remembered as a historic upset.

Facing roughly 1,500 cheering supporters at Atlantic Aviation, Mr. McCain continued the anti-tax message central to his closing campaign argument. He sparked a chorus of enthusiastic "boos" as invoked the now-famous emblem of his campaign, Joe the Plumber.

"Sen. Obama told Joe the Plumber that he wants to spread the wealth around," he said. "Sen. Obama is running to be redistributionist-in-chief; I'm running to be commander-in-chief."

Mr. McCain's entourage included his wife, Cindy, former Gov. Tom Ridge and the Democratic-turned Independent senator from Connecticut he referred to as "Joe the Lieberman," the "most foolhardy and bravest person I've ever know in American politics."

Mr. Ridge and Mr. McCain did their best to enlist another figurative ally in their last-minute campaigning -- let's call him Joe the Coal Miner -- as they seized on a January comment by Mr. Obama, saying that a utility building a new coal plant without anti-emissions technology would go bankrupt under the cap-and-trade system he advocates to control greenhouse gases.

"He's not only going to raise your taxes; he's going to raise your electricity bills," Mr. Ridge said as he characterized the Democrat as a mortal threat to the coal industry. "We're not only going to drill, baby, drill, we're going to dig, baby, dig."

The Obama campaign met the new line of attack, also pressed in automated phone calls in coal producing states, with a statement maintaining that Mr. Obama's words had been taken out of context.

The platforms of both candidates call for billions of dollars in investment in clean coal research, and both have called for some form of cap-and-trade system to limit emissions while charging polluting industries that exceed those caps. Neither has spelled out precise details and figures on how that what that would work in practice.

As he campaigned through states carried by President Bush four years ago, Mr. Obama blistered the Republican on the economy.

Campaigning in Jacksonville, hours after he received the news that the grandmother who helped raise him had died of cancer, Mr. Obama said, "John McCain actually came here, to Veterans' Memorial Arena, and repeated something he's said at least 16 times on this campaign. He said -- and I quote -- 'the fundamentals of our economy are strong.'"

From Jacksonville, in a state whose loss would all but doom the Republican's chances of forming an Electoral College majority, the Democrat traveled on to rallies in North Carolina and Virginia, two other recently Republican states made competitive by his aggressive and lavishly funded campaign.

The nominee's wife, Michelle Obama, was also campaigning in red states -- Nevada and Colorado, while the Democrats' vice presidential candidate, Sen. Joseph R. Biden Jr., who made stops in Missouri and Ohio, was to end his final day of campaigning prodding turnout among Democratic voters in Philadelphia.

Crowd size is not an unreliable predictor of voting results -- Mr. Obama addressed one of the largest rallies in Pennsylvania political history in Philadelphia the night before he lost the state's primary to Sen. Hillary Rodham Clinton -- but the Democratic side's confidence has been stoked by the continuing imbalance in the numbers of voters attracted to their closing rallies.

Mr. McCain's crowds in the closing weeks have typically ranged from 1,000 to 5,000, although he drew a reported 10,000 to a late-night rally in Miami Sunday. Mr. Obama's crowds consistently number in the tens and scores of thousands.

There is an apples-and-oranges element to a comparison of the last Western Pennsylvania crowds to see the candidates. Mr. Obama's Mellon Arena rally last week took place after the work day in a site accessible to public transportation and in walking distance of many workers and residents. Nonetheless, the Democrat drew 10 times the crowd that greeted Mr. McCain at midday yesterday.

While most public attention was focused on the candidates themselves, their fates were being shaped by the intense ground games pursued by their campaigns in these final hours. Such grass-roots get-out-the-vote efforts were the forte of the Obama campaign throughout the primaries and, in state after state, the extent of the paid and volunteer organizational efforts were described as unprecedented.

Craig Schirmer, Mr. Obama's Pennsylvania director, reported in a memo yesterday that over the campaign's final weekend, his campaign's field staff and volunteers had knocked on 1,811,801 doors in the state, and made 1,193,573 phone calls to voters. Republican officials maintained that their voter contacts were well ahead of the widely praised effort that helped re-elect President Bush four years ago, but the GOP, in Pennsylvania and other states, appeared to be at a clear deficit in manpower and organizational strength.

Many analysts predicted that the product of such efforts along with the intense interest in the campaign would be a record voter turnout.

The previous voting record was 122 million set four years ago. Bill McInturff, Mr. McCain's pollster, said that today's turnout could exceed 130 million, bringing long lines to polling places.

The dramatic presidential plot lines absorbed the attention that in other years might go to sharply contested races farther down on the nation's ballots.

Democrats were hoping for big gains in both houses of Congress. Several longtime GOP senators appeared to be in jeopardy, including Sens. Elizabeth Dole in North Carolina and Mitch McConnell in Kentucky. Republican House members also faced stiff political headwinds across the county. In Pennsylvania, the veteran Erie lawmaker Rep. Phil English was in the fight of his political life against Democratic newcomer Kathy Dahlkemper.

In an exception to the tide against the Republicans, two prominent Pennsylvania Democrats, Rep. John Murtha, D-Johnstown, and Paul Kanjorski, D-Luzerne, were battling for survival.

In Pennsylvania, Republican Attorney General Tom Corbett faced a challenge former Democrat John Morganelli, and Marakay Rogers, a Libertarian. Democratic Auditor General Jack Wagner was opposed by Chet Beiler and Libertarian Betsy Summers. Vying for the open seat for Treasurer are Democratic nominee Rob McCord, Republican Tom Ellis and Libertarian Berlie Etzel.

All state House seats were on the ballot along with half of the state's Senate seats. The Republicans' majority in the Senate appeared secure but control of the House hangs in the balance as the Democrats defend their one-vote majority.

With that margin, any state House race could be crucial, but the most dramatic story line focused on the southwest corner of the state where Majority Leader and former Speaker Bill DeWeese was defending a seat against Republican Greg Hopkins. He narrowly defeated Mr. Hopkins two years ago.