Updated Tuesday, November 6, 2012 at 07:47 PM
After billions of dollars, hours of debates and frantic last-minute pitches from the candidates, it's up to the voters Tuesday to decide whether to give President Obama a second term or change course with Republican Mitt Romney.
Also at stake is control of Congress. Thirty-three Senate seats and all 435 House of Representatives seats are up this year, and while the House is expected to remain in Republican hands, Senate control hinges on a host of tight races.
Turnout will be one key to handicapping who's winning the White House and congressional battles, heading a long list of unknowns. Will the relentlessly negative campaign help or hurt? Did Hurricane Sandy benefit the president? Did early voting give him a big advantage?
Once the polls close starting at 3 p.m. PST in Indiana and Kentucky, a number of early clues will signal whether Obama or Romney will get the 270 electoral votes needed to win. Polls Monday continued to show the race a virtual tie nationally and in most of the 11 battleground states.
The first hints of how the night might go will come in four early poll-closing states: Virginia, North Carolina, New Hampshire and Indiana. Obama won all four in 2008.
Romney needs all four if he's to become the sixth person in 100 years to defeat a sitting president. Should he falter in even one, or the results become too close to call, this race won't be over quickly.
Obama, on the other hand, can score an important win early by taking Florida. Losing its 29 electoral votes would be a huge blow to Romney, who has pushed hard for the state's votes and began his last full campaign day Monday in Orlando.
If exit polling indicates Romney is substantially exceeding the share of the white vote that went to Sen. John McCain four years ago, that will be a sign that he is replicating the coalition that gave President George W. Bush a second term. And in Ohio, the vote in Hamilton County, which Obama and Bush both won, could signal who takes the state.
Romney's campaign built its theory of winning around the idea that turnout for Obama will fall well below his 2008 tally. The Obama campaign did not entirely disagree, but it believes it has rebuilt his coalition of women, Hispanics, African Americans and young voters with just enough to win.
Turnout was expected to be down somewhat from 2004 and 2008, according to models developed by the Gallup Organization. Voters "have not been quite as engaged" in the election, a Gallup analysis said, and many voters could be distracted by Hurricane Sandy, whose impact is still being felt in parts of the Northeast.
Most states are solidly for Obama or Romney, so 11 are likely to decide the race.
As the night unfolds, here's how to watch the returns:
Hour by hour
4 p.m.: Polls close in six states but all eyes will be on Virginia, the first of the battleground states to begin reporting results. Obama's 2008 victory was the first there by a Democratic presidential candidate since 1964. Virginia typically has been fairly fast at counting ballots. But there's a new voter ID law in the state that could complicate things this year. Voters who don't bring identification to the polls still can have their ballots counted if they produce ID by Friday. If the race in Virginia is super tight, it could come down to those provisional ballots. On election night, no one will even know how many of them are out there. Keep an eye on turnout in northern Virginia's Democratic strongholds for an early idea of which way the state will go.
4:30 p.m.: Ohio, North Carolina. Romney needs Ohio and its 18 electoral votes; no Republican has won the White House without the state. North Carolina is another state Obama won in 2008, the first time a Democrat had taken it in decades, but Romney is counting on winning its 15 electoral votes. If not, he's probably in trouble. If Ohio is particularly close, and polls suggest it might be, there's a chance the outcome there won't be known until after Election Day, and the presidency could hinge on it. In the last several elections, 2 percent to 3 percent of the state's votes came from provisional ballots, which aren't counted until later. In 2004, after a long, tense night counting votes, the presidential race wasn't decided until 11 a.m. the next day, when Democrat John Kerry called President George W. Bush to concede Ohio and the presidency.
Without Ohio, Romney would need victories in nearly all the remaining up-for-grabs states and he'd have to pick off key states now leaning Obama's way, such as Wisconsin and Iowa. Obama has more workarounds than Romney if he can't claim Ohio.
If Romney carries Ohio, viewers should settle in for a long night. A Romney victory there could signal that the vaunted ground organization of the Obama campaign is faltering and that his Midwestern firewall is cracking.
The television networks — and their high-tech maps — will spotlight the three C's of Ohio: Cleveland, Columbus and Cincinnati. The president is looking for a strong performance in Cleveland, which Romney is visiting Tuesday in the hope of shaving down Democratic margins. And Republicans are looking for strength in Cincinnati and its surrounding area of Hamilton County; when Obama won the county in 2008, he was the first Democrat in a generation to do so.
5 p.m. : New Hampshire, Florida, Pennsylvania. If Obama wins Florida, Romney's chances would get shakier. But if Romney wins Pennsylvania's 20 electoral votes, which Obama has regarded for months as his, the president should start worrying. The four electoral votes of New Hampshire — Democratic in the past two elections — matter if the race stays close. More pieces of the puzzle will start falling into place as polls close in the District of Columbia and 16 states, including battlegrounds Florida (29) and New Hampshire (four).
Democratic-leaning parts of Florida tend to be the last places to report, so be careful about jumping to a conclusion if Romney looks strong early on. The ballot in many counties is unusually long, running more than 10 pages in some areas of the state because of judicial elections and initiatives, which means voting could take longer. And long lines in Florida could mean a long night ahead for Obama and Romney.
Most of the polls in Florida close at 4 p.m. PST, so by 5 p.m. PST, when the last polls close, results will start to roll out quickly. But fully 4.5 percent of votes in Florida weren't counted on election night in 2008, so if things are tight, no one's going to be hasty about declaring a victor in the state. Especially after the 2000 fiasco in which the winner in Florida, and thus the presidency, wasn't determined for more than a month. If you want to get really granular, Hillsborough County, home to Tampa, is widely considered a bellwether for the state.
Also keep watch on Pennsylvania for any signs of a Romney surprise. The state has long been considered safe for Obama, but Republicans started running ads there in the final week of the campaign and Romney campaigned there Sunday. No Republican presidential candidate has carried the state in nearly a quarter century. If the television networks are not able to call Pennsylvania quickly, Democrats have reason to move to the edge of their seats.
6 p.m.: Wisconsin, Colorado, Michigan. A Romney win in Michigan — a state Obama won last time by 16 percentage points — would be another sign that the president is faltering. Wisconsin and Colorado are toss-ups. Polls close in 14 states, including battlegrounds Colorado (nine) and Wisconsin (10). Democrats have carried Wisconsin for six straight presidential elections and Obama had the edge in polling going in, so a flip here would be especially noteworthy.
Historically, as much as 10 percent of Colorado's vote doesn't get counted on election night, and those ballots could be decisive in a close race.
Information from exit polls could help flesh out the Colorado picture: Young professionals and Hispanic voters were central to Obama's victory there in 2008, but the sluggish economy has hurt his standing.
Two more to watch: Minnesota and Michigan. The states long have been considered safe for Obama, but the Republicans made late moves there.
7 p.m.: Iowa, Nevada. Nevada has been trending Democratic. A strong Latino turnout would be a signal that Obama is doing well. Iowa is another tossup. Iowa's been leaning toward Obama, but watch how the vote breaks down geographically. Can Romney's advantage in GOP-heavy western Iowa overcome Obama's edge in eastern swing territory? Polls close in four states, including the last of the battlegrounds, Iowa (six) and Nevada (six).
8 p.m.: Polls close in five western states, but most are foregone conclusions for Obama. He gets 78 electoral votes from California, Hawaii, Oregon and Washington; Romney gets four from Idaho.
10 p.m. The last of the polls close, in Alaska. Romney gets three electoral votes. Will many people still be up? Political junkies could well be waiting to see how things play out in one or more battleground states.
Turnout. Conventional wisdom says Democrats tend to dominate early voting, while Republicans do better on Election Day, so a big turnout could mean a big day for Romney.
Latino voting. Tuesday marks the culmination of four years of registering new voters in hopes of harnessing growing Latino clout and finally shattering the reputation that Latinos are apathetic voters who can be ignored. In 2008, 50 percent of eligible Latino voters cast ballots, compared with 65 percent of blacks and 66 percent of whites, according to the Pew Hispanic Center.
The National Association of Latino Elected and Appointed Officials estimates that 12 million Latino voters will visit the polls in this year's election, which would be a 26 percent increase from 2008. More than 3 million Latinos are expected to vote in their first presidential election. A big turnout could mean the difference in Colorado, Nevada and perhaps Arizona.
Long lines. Polls might stay open past closing time, delaying the vote count. But if lines are too long and people get discouraged, they might go home.
Hurricane Sandy. Will voters be more sympathetic to Obama in hard-hit states such as Pennsylvania or New Hampshire? Or blame the feds for being too slow to respond?
One of the night's most unpredictable cliffhangers involves control of the Senate.
Democrats now control 53 of the 100 seats, and they're defending 23 to the Republicans' 10. Close races in Virginia, Indiana and Massachusetts might offer early hints as to whether Republicans can achieve the net gain of four — three, if Romney is elected — to win control.
The next group of close races is farther west, notably in Montana, Nevada and Arizona.
In the House, Democrats need a net gain of 25 for control, but independent analysts don't expect the party to gain more than 10.
Compiled from McClatchy Newspapers, The Associated Press and The New York Times
JUSTIN SULLIVAN / GETTY IMAGES
Supporters of Mitt Romney wave American flags at a campaign rally Monday in Columbus, Ohio. No Republican has won the White House without carrying Ohio. Without Ohio, Romney would need victories in nearly all the remaining up-for-grabs states and he'd have to pick off key states now leaning Obama's way.