PITTSBURGH — With two wars and an economic calamity as backdrop, U.S. voters were poised to make history today, electing either the nation's first black president or its first female vice president.

Democrat Barack Obama was leading in polls in more than enough states to garner the 270 electoral votes needed to capture the White House, including some that have been Republican for a generation or more.

His travels yesterday, shadowed by the death of his grandmother in Hawai'i, illustrated Obama's advantage. He went to three states — Florida, North Carolina and Virginia — that President Bush won in both his elections, underscoring how dramatically the nation's political landscape has shifted in the past four years.

Fighting to catch up, Republican John McCain dashed across seven states, starting in Florida and ending, more than 20 hours later, in his home state of Arizona, where late polls showed a tightening contest. Except for Pennsylvania, which last voted Republican in 1988, McCain spent his day defending states in Bush's column in 2004.

A record 130 million or more Americans are expected to cast ballots in an election that has captivated the country like no campaign in decades, drawing stadium-size crowds and bigger TV ratings than both "American Idol" and baseball's World Series.

Both sides were on guard — their lawyers standing by — watching for voting irregularities after two presidential elections marked by balloting controversies. Yesterday, there were scattered reports of dirty tricks, including a leaflet passed around black neighborhoods of Philadelphia, saying police would be at the polls to arrest anyone with unpaid parking tickets.

27 MILLION EARLY VOTES

For some, Election Day has come and gone. More than 27 million votes have been cast in 30 states, a record turnout driven by the candidates' exhaustive get-out-the-vote efforts and the prospect of history happening no matter who wins. A McCain victory would install Alaska Gov. Sarah Palin in the highest elected office held by a woman. A win by Obama would hurdle the country's ultimate racial barrier.

Bouncing between states, the presidential hopefuls returned to themes honed to a fine point after more than two years of campaigning, dozens of debates and hundreds of millions of dollars in radio and TV advertising.

"John McCain just doesn't get it," Obama told a crowd in Jacksonville, Fla., assailing his opponent for opposing tougher regulation of Wall Street and supporting Bush's economic policies. "They haven't worked. It's time for change, and that's why I'm running for president."

McCain portrayed Obama as too liberal and inexperienced to reverse the country's course, at a time when more than eight in 10 Americans tell pollsters the country is headed the wrong way. The same polls show the economy is by far the top concern of voters, supplanting the war in Iraq, which once figured to be the main campaign issue.

"If we're going to change Washington, we need a president who has actually fought for change and made it happen, even by taking on the leaders of his own party," McCain told a crowd of 1,000 supporters in a hangar at the Pittsburgh airport. "He has stayed in the far-left lane of American politics. The next president won't have time to learn how to change Washington or get used to the office."

BUSH KEEPS LOW PROFILE

Bush was nowhere to be seen yesterday, underscoring the toll his unpopularity has taken on McCain and his fellow Republicans.

"We're realistic about the political environment we're in," White House press secretary Dana Perino said of the president's absence.

Bush's low profile was deliberate, she said, because Republicans "wanted to make this election about John McCain."

It was Obama who brought up the president throughout the day, mocking his rival's effort to cast himself as a reformer.

McCain "hasn't been a maverick," Obama said in Jacksonville, his day's first stop. "He's been a sidekick to George Bush."

McCain, for his part, continued to question Obama's preparedness, citing a prediction from his running mate, Delaware Sen. Joe Biden, about the early days of an Obama administration.

"He warned that Sen. Obama would be tested with an international crisis within the first six months due to his youth and inexperience, and at the same time Democrats in Congress are talking about deep defense cuts," McCain told a crowd of about 1,000 in Tampa, Fla., drawing a chorus of boos. "We have troops fighting in two wars and the Democrats' answer is to lower our defenses and put someone in office who our enemies will test? I've been tested! I passed that test! Sen. Obama has not."

EARLY PROJECTION?

Even with the dawn of Election Day, the two candidates had no plans to let up. Obama scheduled a quick hop from Chicago to Indiana before winding up with a massive rally today along the Chicago lakefront. McCain had events scheduled in Colorado and New Mexico before returning to Phoenix to watch the returns and host a party.

The first states to finish voting are Indiana, Virginia and a handful of others, followed by North Carolina and Ohio. The TV networks do not plan to wait for all the polls to close nationwide before projecting a winner, if possible, but news executives said it was unlikely that either candidate would have 270 electoral votes before the polls close in the West.

An early projection of Ronald Reagan's 1980 landslide victory caused a storm of protest from Democrats, who said the forecast dampened turnout and cost the party a number of races in California and elsewhere.