Buoyed by cheering crowds and bolstered by more than $1.3 million a day in TV ads, Democrats Barack Obama and Hillary Rodham Clinton raced through the final hours of an unpredictable Super Tuesday campaign across 22 states. The Republican race turned negative on the eve of the busiest day in primary history.

"We're going to hand the liberals in our party a little surprise," boasted Mitt Romney, the former Massachusetts governor, criticizing John McCain for his positions on tax cuts, gay marriage and immigration and predicting an upset win in delegate-rich California.

McCain struck back a few hours later Monday with a television ad that showed Romney in a 1994 debate against Democratic Sen. Edward M. Kennedy, saying he was "an independent during the time of Reagan-Bush. I'm not trying to return to Reagan-Bush."

Outwardly, McCain projected confidence, not only about wrapping up the nomination but about November's general election as well. "I can lead this nation and motivate all Americans to serve a cause greater than their self-interest," he said while campaigning at a fire station in New Jersey.

Unwilling to leave anything to chance, both men hastily rearranged their schedules to make one more late stop in California, the largest state, with 170 delegates.

After months on the road, the wear on the candidates was showing, and the schedules strained human endurance.

Clinton's voice was raspy, and at one stop, she struggled to control her coughing.

Romney had breakfast in Tennessee, was in Georgia at lunchtime, touched down in Oklahoma at the dinner hour and arrived in California for a rally with 1,000 cheering supporters in Long Beach just before midnight Eastern time.

He then was flying through the night so he could attend the West Virginia state convention Tuesday morning.

The Democrats were spending unprecedented amounts of money on television advertising. Records showed Obama and Clinton each spent $1.3 million last Wednesday and have been increasing their purchases in the days since.

Obama spent about $250,000 to run a 30-second ad during the Super Bowl in selected, less expensive regions. Clinton turned talk-show host Monday night, buying an hour of time on the Hallmark Channel to televise a town hall meeting from New York in the Super Tuesday states. With husband Bill and daughter Chelsea on camera in other locations, she took questions from voters beamed in from far-flung locales including Fargo, N.D., Knoxville, Tenn., and Albuquerque, N.M.

The prize in each race was a huge cache of delegates on the biggest primary-season day ever.

In all, there are 1,023 delegates to the Republican National Convention at stake in primaries in 15 states, caucuses in five and the West Virginia state convention.

Several award all their delegates to the winner, and McCain was favored in New York, New Jersey, Connecticut, Delaware and his home state of Arizona, with 251 delegates combined.

Romney hoped to counter with victories in Utah and West Virginia, as well as in a string of caucuses in Western and Midwestern states.

But his task in several Southern and border states -- Arkansas, Alabama, Georgia, Oklahoma and Missouri -- is complicated by the presence of Mike Huckabee on the ballot.

The former Arkansas governor was in Tennessee, where he said Wal-Mart Republicans knew long before Wall Street that the economy was headed for trouble. "They were paying more for their fuel and more for their health care and their kids' education, but their paychecks weren't going up enough to cover all those things that were costing more," he said.

In sheer numbers, Democrats have more at stake than Republicans -- 15 primaries, and caucuses in seven states plus American Samoa, and 1,681 delegates.

They also lack a clear front-runner in the historic race between Clinton, who is trying to become the first woman to sit in the White House, and Obama, seeking to become the first black commander in chief.

The Northeast was their battleground for the day, an arc of states stretching from New Jersey and New York to Connecticut and Massachusetts. Apart from Clinton's home state of New York, the polls told a similar story in each -- and in Missouri and California -- with the former first lady trying to hold off Obama's late rush.

Obama's campaign was eager to claim the underdog's role. "Senator Clinton is certainly the favorite on Feb. 5, given the huge leads she has held in many of these contests throughout the course of the campaign and the political, historical and geographic advantages she enjoys in many of these states," Obama's campaign manager, David Plouffe, wrote in a memo to reporters.

In a conference call with reporters, Clinton strategists Howard Wolfson and Mark Penn predicted she would emerge from Super Tuesday with more delegates than Obama. But they agreed the race is far from over. "Many of us will be making our reservations for Texas and Ohio and perhaps Pennsylvania and beyond that," Wolfson said, speaking of contests taking place in March and April.

Clinton's first stop Monday was in New Haven, where she graduated from Yale Law School more than three decades ago.

Penn Rhodeen, a public interest lawyer who worked with Clinton as a student, recalled her showing up on his doorstep wearing purple bellbottoms.

"It was so 1972," he recalled, praising Clinton for her longtime interest in helping children.

"Here is the abiding truth we know -- you have always been a champion for children. Welcome home, dear friend. We are so proud of you."

Clinton briefly grew emotional, wiping her eyes with her hand. "I said I would not tear up. Already we're not on that path," she said to laughter.

Obama campaigned in New Jersey within sight of the Meadowlands, home of the New York Giants, who defeated the previously unbeaten New England Patriots on Sunday night to win the Super Bowl. "Sometimes the underdog pulls it out," he said, talking about himself as much as a football team. "You can't always believe the pundits and prognosticators."

With so many states to cover, and so little time, the candidates relied on surrogates to expand their reach.

Former President Clinton spoke before a large number of Hispanic students at Santa Ana College in California, where he said he was part of the reason they should vote for his wife. "You know we have always been there for you, in good times and bad, we've been there for California," he said.

Obama campaigned with Sen. Edward M. Kennedy at his side, trying to close once-large gaps in the polls in the Northeast, including the senator's home state of Massachusetts.

Former Sen. Rick Santorum of Pennsylvania, campaigning alongside Romney, told reporters that if voters "want a conservative as the nominee of this party, you must vote for Mitt Romney. Because Mitt Romney is the only person in this race that can stop John McCain and the elite in the party who don't as much care about those issues that a lot of folks in Georgia care about."

But former Sen. Bob Dole, the party's 1996 presidential candidate, came to McCain's defense. "Whoever wins the Republican nomination will need your enthusiastic support," he wrote conservative radio host Rush Limbaugh, who has been critical of McCain. "Two terms for the Clintons are enough."

Largely overlooked in the chaos of the campaign was the opening of voting for Democrats living overseas in more than 30 countries. The first ballots to pick delegates were cast at midnight in Indonesia, where Obama lived as a child.