WASHINGTON  — President Barack Obama and former Massachusetts Gov. Mitt Romney dueled for the White House on Tuesday, the tight-to-the-finish climax of an election persistently shadowed by a weak national economy and high unemployment that crimped middle class dreams for millions.

Voters also chose a new Congress to serve alongside the man who will be inaugurated president next January, Democrats defending their majority in the Senate, and Republicans in the House. Eleven states picked governors, and ballot measures ranging from gay marriage to gambling dotted ballots.

The long campaign's cost soared into the billions, much of it spent on negative ads, some harshly so.

In the presidential race, an estimated one million commercials aired in nine battleground states where the rival camps agreed the election was most likely to be settled — Ohio, New Hampshire, Virginia, Florida, North Carolina, Wisconsin, Iowa, Colorado and Nevada. Those states accounted for 110 of the 270 electoral votes needed for victory, and they drew repeated appearances by the 51-year-old president and Romney, 65.

There was one last startling sight on Election Day, which turned out to be the last campaign day, as well. In Ohio, crucial to the end, Romney waited on his plane at the Cleveland airport for running mate Paul Ryan to arrive for a joint campaign appearance as Vice President Joe Biden's plane took off following his own event. Romney told Richmond, Va., radio station WRVA, "I can't imagine an election being won or lost by, let's say, a few hundred votes and you spent your day sitting around."

Obama made get-out-the-vote calls from a campaign office near his home in Chicago and found time for his traditional Election Day basketball game with friends. Addressing his rival, he said, "I also want to say to Gov. Romney, 'Congratulations on a spirited campaign.' I know his supporters are just as engaged, just as enthusiastic and working just as hard today." Romney, in turn, congratulated the president for running a "strong campaign."

Other than the battlegrounds, big states were virtually ignored in the final months of the campaign. Romney wrote off New York, Illinois and California, while Obama made no attempt to carry Texas, much of the South or the Rocky Mountain region other than Colorado.

There were 33 Senate seats on the ballot, 23 of them defended by Democrats and the rest by Republicans.

The GOP needed a gain of three for a majority if Romney won, and four if Obama was re-elected. Neither Majority Leader Harry Reid of Nevada nor GOP leader Mitch McConnell of Kentucky was on the ballot, but each had high stakes in the outcome.

All 435 House seats were on the ballot, including five where one lawmaker ran against another as a result of once-a-decade redistricting to take population shifts into account. Democrats needed to pick up 25 seats to gain the majority they lost two years ago.

Speaker John A. Boehner, R-Ohio, raised millions to finance get-out-the-vote operations in states without a robust presidential campaign. His goal was to minimize any losses, or possibly even gain ground, no matter Romney's fate. House Democratic leader Rep. Nancy Pelosi of California campaigned aggressively, as well, and faced an uncertain political future if her party failed to win control.

In gubernatorial races, Republicans hoped to gain seats after Democratic retirements in New Hampshire, Washington, Montana and especially North Carolina.

Obama awaited the results in Chicago, where he ended his campaign with a huge election eve rally on Monday.

Romney was in Massachusetts after his Election Day dash to Ohio and Pennsylvania.

In a campaign that traversed contested Republican primaries last winter and spring, a pair of political conventions this summer and three presidential debates, Obama, Romney, Biden and Ryan spoke at hundreds of rallies, were serenaded by Bruce Springstein and Meat Loaf and washed down hamburgers, pizza, barbecue and burrito bowls.

Obama was elected the first black president in 2008, and four years later, Romney became the first Mormon to appear on a general election ballot. Yet one man's race and the other's religion were never major factors in this year's campaign for the White House, a race dominated from the outset by the economy.

Over and over, Obama said that during his term the nation has begun to recover from the worst recession since the Great Depression. While he conceded progress has been slow, he accused Romney of offering recycled Republican policies that have helped the wealthy and harmed the middle class in the past and would do so again.

Romney countered that a second Obama term could mean a repeat recession in a country where economic growth has been weak and unemployment is worse now than when the president was inaugurated. A wealthy former businessman, he claimed the knowledge and the skills to put in place policies that would make the economy healthy again.

In a race where the two men disagreed often, one of the principal fault lines was over taxes. Obama campaigned for the renewal of income tax cuts set to expire on Dec. 31 at all income levels except above $200,000 for individuals and $250,000 for couples.

Romney said no one's taxes should go up in uncertain economic times. In addition, he proposed a 20 percent cut across the board in income tax rates but said he would end or curtail a variety of tax breaks to make sure federal deficits didn't rise.

The differences over taxes, the economy, Medicare, abortion and more were expressed in intensely negative advertising.

Obama launched first, shortly after Romney dispatched his Republican foes in his quest for the party nomination.

One memorable commercial showed Romney singing an off-key rendition of "America The Beautiful." Pictures and signs scrolled by saying that his companies had shipped jobs to Mexico and China, that Massachusetts state jobs had gone to India while he was governor and that he has personal investments in Switzerland, Bermuda and the Cayman Islands.

Romney spent less on advertising than Obama. A collection of outside groups made up the difference, some of them operating under rules that allowed donors to remain anonymous. Most of the ads were of the attack variety. But the Republican National Committee relied on one that had a far softer touch, and seemed aimed at voters who had been drawn to the excitement caused by Obama's first campaign. It referred to a growing national debt and unemployment, then said, "He tried. You tried. It's OK to make a change."

More than 30 million voters cast early ballots in nearly three dozen states, a reflection of the growing appeal of a relatively new phenomenon.

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Associated Press writers Julie Pace in Chicago Philip Elliott in Cleveland contributed to this report.