Democrat Barack Obama said months ago that he intended to compete hard in states that Democratic presidential nominees haven't won in decades.
He's done so well at expanding the battleground that a dozen states could claim bragging rights as most dramatic or decisive in the race between Obama and Republican John McCain.
Some states, such as Ohio, Florida and Missouri, are perpetually under the microscope on election nights because neither party can count on winning them.
Others, including typically Republican Virginia, North Carolina and Nevada, are new to the must-watch list, as polls show Obama leading or competitive.
Television networks won't project a winner in any state until polls there close. They also may be gun-shy about predicting winners based on surveys of voters leaving polling places, because such exit polls turned out to be inaccurate throughout most of Election Day in 2004. That means the networks may not call races until returns start to come in.
As vote tallies and analysis flood television networks and the Web, here's what to watch for tonight in four critical states. All times are Eastern.
7 p.m.: The New Old Dominion
Democrats have long been tempted by the changing demographics in Virginia, which last supported a Democratic nominee in 1964. Since Democrat John Kerry made a brief play for it in 2004, the state has moved from Republican red toward Democratic blue.
Democratic winners have included Gov. Tim Kaine in 2005 and Sen. Jim Webb in 2006.
In this year's Senate race between two former governors, polls show Democrat Mark Warner leading Republican Jim Gilmore by nearly 2 to 1.
Obama, ahead by single digits, made a massive investment in the state. He has three times as many field offices as McCain and last week spent about four times as much on TV ads ($2.5 million vs. $637,000, according to the Wisconsin Advertising Project).
On the final weekend, both men held rallies in the Washington suburbs of Northern Virginia. McCain is trying to stem the blue tide in the diverse, highly educated region that his brother, Joe, joked was "communist country."
Larry Sabato, head of the University of Virginia's Center for Politics, says Obama needs to win the region with 60% of the vote — about 7 points more than Kerry — to win the state.
Counties to watch: Bush won Prince William with 53% and Loudoun with 56%. Obama is looking to flip both and improve on Kerry's 53% in Fairfax County, the largest jurisdiction in the area, with 1 million residents.
Blacks, who made up about one-fifth of Virginia's electorate in 2004, gave Kerry 87% of their votes. Obama could do better. Keep an eye on returns and exit polls in Richmond and Virginia Beach tonight for clues.
McCain's strongholds include military voters around Norfolk and rural voters across southern Virginia. Obama needs to split the Norfolk region with McCain and hold at least 40% of the rural vote to win the state, Sabato says.
Late polls suggest Obama will hold all the states Kerry won and at least pick up Iowa. If that happens, and Obama also picks up Virginia's 13 electoral votes, McCain would have no mathematical path to victory.
"If Virginia goes for Obama, McCain's finished," Sabato says.
7:30 p.m.: Eye on the Buckeye
Ohio, with its 20 electoral votes, is center stage for the second election in a row. No Republican has won the presidency without taking Ohio since Abraham Lincoln did it in 1860.
Team McCain has treated Ohio as "must-win," says Eric Rademacher, co-director of the University of Cincinnati's Ohio Poll. "It's critical to just about any electoral map scenario that they've put together," Rademacher says.
Obama has visited 13 times since winning the Democratic nomination in June.
McCain has visited 18 times and even shaped his closing national argument around "Joe the Plumber" — Joe Wurzelbacher, a critic of Obama's tax plan from a Toledo suburb. Obama, whose website lists 82 Ohio offices (vs. 45 for McCain), was there Sunday with Bruce Springsteen.
Two areas to watch tonight: Wood County south of Toledo, which went for President Bush in the past two elections and Democrat Bill Clinton in the two before; and southwest Ohio, which includes Dayton, Cincinnati and Wright-Patterson Air Force Base.
Grant Neeley, a political scientist at the University of Dayton, says southwest Ohio is "a very right-leaning, conservative" area.
Bush won that part of the state by 10 percentage points. McCain's chances hinge on whether he can hold on there; in the Toledo area, which Kerry and Bush split; and in Columbus and central Ohio, where Bush won by 18 points. The county to watch: Hamilton (Cincinnati), which Bush won 53%-47%.
The hurdles for McCain include a changed political climate. In 2006, GOP scandals helped Democrats pick up a House seat and statewide offices from governor on down. The Wall Street crisis has reinforced sentiment against Republicans, Neeley says.
In addition, Obama also could improve on Kerry's 86% showing among blacks, who accounted for 10% of Ohio voters in 2004.
Across southern Ohio, Neeley says a central question is whether white working-class Democrats "will cross to vote for McCain out of racial prejudice."
The southeast has little industry, he says, while the southwest is in a "huge downturn" and faces a General Motors plant closing Dec. 23.
"Economic reality is bad enough" that people are looking past race, he says. "Conditions are right for Obama to win in Ohio."
8 p.m.: Show-me bellwether
Missouri has backed every presidential winner since 1904, with one exception: It went for Democrat Adlai Stevenson instead of Republican Dwight Eisenhower in 1956.
David Webber, a state politics specialist at the University of Missouri-Columbia, says voters may blow it again "and our bellwether image will be tarnished."
Bush won Missouri by 7 percentage points in 2004. This year the race is even, and both tickets are lavishing time on the state. The principals have been there nine times apiece. Obama drew record crowds last month in St. Louis and Kansas City .
Sen. Claire McCaskill, D-Mo., won her seat in a 2006 squeaker after campaigning extensively in GOP areas. She received 39% of the vote in small cities and rural Missouri, 6 points better than Kerry did two years earlier.
Webber says it's unlikely Obama will match either of those numbers, but he could do better in St. Louis and Jefferson County to its south.
Kerry won 84% of the St. Louis vote and 51% in the suburbs. An Obama uptick also is possible in Kansas City, where Kerry beat Bush 52%-48%.
Boone County, which includes Columbia and went for Bush in 2004, is a key early indicator. Webber says its returns usually come in fast and that "if McCain wins or is within 1,000 votes, it is bad for the Democrats."
Another bad sign for Democrats: if McCain's margins top 50,000 votes in St. Charles County (a GOP exurb of St. Louis) and Greene County in southwest Missouri.
The three areas have been well traveled. McCain's first trip to Missouri after Obama won the nomination in June was to Springfield, in Greene County. Obama's last trip to Missouri, on Saturday, was to Springfield. Last Thursday, he rallied supporters in Columbia. McCain's running mate, Sarah Palin, was just to the south Monday in Jefferson City.
Attorney General Jay Nixon, a Democrat, has a double-digit lead over GOP congressman Kenny Hulshof in the governor's race.
However, Nixon's popularity has not sparked an Obama surge; nor have Obama's many field offices (42 to McCain's 16) and forays into conservative areas.
Missouri is less diverse than other battleground states, Webber says, and the state "seems to be slower to respond to Obama."
10 p.m.: Silver State shifts
Nevada, New Mexico, Arizona and Colorado make up a new, fast-growing swing region in the Mountain West.
Both tickets have visited three of the four states numerous times. The Obama camp has said Arizona would be in play if it weren't McCain's home state.
Bush won Nevada 50%-48% in 2004. But Democrats, slightly behind in voter registration back then, now have more than a 100,000-voter advantage.
Obama and McCain are near parity on state offices, but Obama has visited more often since June and has been building his turnout operation since the hard-fought caucuses against Hillary Rodham Clinton early this year.
Palin and McCain scheduled election-eve rallies in Reno, Elko and Henderson, but more than half the state's registered voters already had voted.
Independent analyst Jon Ralston says early votes and absentee ballots will be released shortly after poll closing.
"If Obama has a lead of more than 50,000 after early voting, that will be very difficult for Republicans to overcome," he says.
If the early numbers are inconclusive, watch the tally in Reno and Washoe County. Kerry lost Washoe by about 7,000 votes at a time when the GOP registration edge was 18,000. Now, Democrats have drawn even.
The other population center is the Las Vegas area, heavily Democratic and home to nearly three-quarters of Nevadans. Ralston says Kerry lost the state four years ago because he didn't turn out enough supporters there.
Hispanics are close to one-quarter of Nevada's population but accounted for only 10% of the vote in 2004, an exit poll showed. More Hispanics this year can vote, Ralston says, and Obama is doing a better job of reaching out to them.
Nevada had the nation's highest foreclosure rate last year and the financial collapse has hit its hospitality and construction sectors hard. Hispanics are disproportionately affected, Ralston says.
But, he adds, "They started coming on board (for Obama) before the economy tanked."