Updated at 12:44 a.m. ET: The Romney campaign tells CBS News the Republican candidate has called President Obama and conceded the race.
Updated at 12:35 a.m. ET: CBS News projects President Obama will win Virginia.
Updated at 11:35 p.m. ET: President Obama is projected to win Nevada.
Updated at 11:16 p.m. ET: President Obama is projected to win Ohio, giving him more than the 270 electoral college votes needed to win re-election.
Updated at 11:12 p.m. ET: CBS News projects President Obama wins the key state of Iowa's six electoral votes, as well as Oregon's seven electoral votes.
Updated at 11 p.m. ET: CBS News projects Mitt Romney will win North Carolina, making it the first battleground state to fall into his column. Romney is also projected to win Idaho.
President Obama, meanwhile, is projected to win California, Hawaii, New Mexico and Washington state.
Updated at 10:50 p.m. ET: Right now, CBS News' Dean Reynolds reports, President Obama is leading in three significant north central Ohio counties with an older, whiter population -- but one that retains ties to the auto industry and organized labor. Mr. Obama won those counties -- Wood, Sandusky and Ottawa counties -- in 2008, and he is winning them again.
Furthermore, a top official from the Ohio secretary of state's office tells Reynolds there are more outstanding votes from urban areas than rural. This is another good sign for Mr. Obama, since urban areas are typically Democratic. An Obama campaign source says they have met their early voting projections, Reynolds reports. Ohio, the source said, is looking good.
Meanwhile, in Virginia, an Obama campaign spokesperson tells CBS News' Nancy Cordes turnout will exceed 2008 turnout, which is a good sign for the president.
Updated at 10:30 p.m. ET: CBS News projects President Obama will win Minnesota, bringing his projected electoral tally at this point to 167. CBS News projects Mitt Romney will win Arizona, bringing his tally to 184.
Updated at 10:15 p.m. ET: CBS News projects the battleground state of Iowa is leaning toward President Obama.
Updated at 10:08 p.m. ET: CBS News projects Mitt Romney will win Missouri, bringing his electoral college tally to 173.
Updated at 10 p.m. ET: CBS News projects Mitt Romney will win Utah and Montana, bringing his electoral college tally to 162.
According to projections, Mr. Obama's electoral college tally stands at 157.
The battleground state of Nevada, where polls are closed, is now leaning toward Mr. Obama. Polls have also closed in the battleground state of Iowa, but CBS News cannot yet project the outcomes there.
Iowa, with six electoral votes, gave Mr. Obama his first big victory in the 2008 caucus, and he won the state in the 2008 general election by 9.4 points. Several factors help explain why the state, which has historically been so kind to Mr. Obama, remains tight, according to CBS News consultant Jeanne Zaino.
While CBS News' early exit polling shows that women favor Mr. Obama by a large number (14 points), his support among men is down seven points from 2008. Similarly, while young people aged 18-29 favor the president (56 percent to 40 percent), those 64 and older favor Mitt Romney.
In the rural and suburban areas which may decide this race, Romney is outperforming Mr. Obama. At the same time, however, independents -- which are key to electoral victory -- are breaking 53 percent to 43 percent for Mr. Obama.
Nevada carries six electoral votes. Mr. Obama won the state by 12.5 points in 2008, and CBS News consultant Stanley Feldman explains that Democrats are coming out in full force for him again: According CBS News early exit polling, 38 percent of voters said they think of themselves as Democrats compared to 29 percent Republican.
Updated at 9:32 p.m. ET: CBS News projects President Obama will win Wisconsin and its 10 electoral votes, as well as New Hampshire's four electoral votes.
Mr. Obama's projected electoral vote tally now stands at 157 while Mitt Romney's stands at 153.
In 2008, Mr. Obama won Wisconsin by 13.9 percent. The state hasn't gone red in a presidential election since 1984. Even with Wisconsin Rep. Paul Ryan on the ticket, Romney faced a steep challenge in his fight for the Badger State. However, Wisconsin has been a hotbed of partisan discord in recent years and Republicans saw huge gains at the state level in 2010.
New Hampshire has just four electoral votes, but it is one of the most competitive states in the nation -- it's the only state that George W. Bush won in 2000 but lost in 2004. In 2008, Mr. Obama won the Granite State by 9.6 percent.
Updated at 9:20 p.m. ET:CBS News projects President Obama will win Pennsylvania's 20 electoral votes, bringing his projected electoral vote tally so far to 143. Mitt Romney's projected electoral vote tally stands at 153.
Additionally, the battleground of New Hampshire is now leaning toward Mr. Obama.
Updated at 9 p.m. ET: CBS News projects President Obama will win Michigan -- the state where Mitt Romney was born and where Romney's father served as governor. Additionally, CBS News projects the battleground of Wisconsin is leaning toward the president.
Mr. Obama is projected to win New York. His projected electoral vote tally now stands at 123.
CBS News projects Romney will win Kansas, Louisiana, Nebraska, North Dakota, South Dakota, Texas and Wyoming. His projected electoral vote tally stands at 153.
Polls have closed in the battleground state of Colorado, but CBS News cannot make any projections there at this time. Polls have also closed in Arizona and New Mexico.
The fight for Colorado's nine electoral votes has remained tight since the early stages of the 2012 general election. George W. Bush took the state in both 2000 and 2004, but with momentum coming out of the 2008 Democratic National Convention, held in Denver, then-candidate Obama claimed the mantle. He beat Sen. John McCain by 8.95 percent.
Updated at 8:41 p.m. ET: Mitt Romney is projected to win Arkansas' six electoral votes, bringing his total projected tally to 88.
The state of Virginia has temporarily suspended the reporting of results because still hundreds, if not thousands, of people are in line to vote. Under state rules, if a voter was in line by 7 p.m. ET, he or she is entitled to vote, no matter how long it takes.
Updated at 8:25 p.m. ET: CBS News projects the key battleground of Ohio is leaning toward President Obama.
Mr. Obama is projected to win New Jersey's 14 electoral votes, bringing his projected total to 78.
Updated at 8 p.m. ET: President Obama is projected to win Connecticut's seven electoral votes, the District of Columbia's three electoral votes and Delaware's three electoral votes. Mr. Obama is also projected to win Illinois' 20, Maryland's 10, Massachusetts' 11 and Rhode Island's four electoral votes. Mr. Obama is also projected to win three of Maine's electoral votes (a fourth is divided proportionally).
That brings Mr. Obama's projected electoral vote tally to 64 so far.
Mitt Romney, meanwhile, is projected to win Mississippi's six electoral votes, Oklahoma's seven, Tennessee's 11, Georgia's 16 and Alabama's nine votes. That brings his projected electoral vote tally to 82.
Polls are now closed in the key states of Florida, New Hampshire and Pennsylvania, but CBS News cannot project a winner in any of those states yet. Polls are also closed in Missouri and New Jersey.
Florida, with its 29 electoral votes, is considered a must-win state for Romney. The state boasts a large population of seniors, which tend to favor Republicans, as well as a diverse Latino population - among which includes a large number of Cuban-Americans, who tend to skew more Republican than most Latino voters. In 2008, Mr. Obama won the state by 2.8 percent. Former President George W. Bush, however, won the state by 5 points in 2004.
New Hampshire has just four electoral votes, but it is one of the most competitive states in the nation.
Pennsylvania has a solid recent history of backing Democratic candidates for president: The state hasn't voted for a Republican presidential contender since 1988, and Mr. Obama beat Republican nominee John McCain by a 10.3-point margin in 2008. With 20 electoral votes, the state represents a critical component to the Obama campaign's path to electoral victory. In recent weeks, however, what looked like a safe lead for the president there appears to have eroded slightly, and the Romney campaign made a last-minute play for support in the state.
Updated at 7:42 p.m. ET: CBS News is projecting Mitt Romney has won South Carolina and its nine electoral votes, bringing his electoral vote tally to 33.
Updated at 7:30 p.m. ET: Polls are closed in the battleground states of Ohio and North Carolina, but CBS News cannot project a winner in either state. The battleground state of Virginia, where polls closed at 7 p.m., remains a toss up as well.
CBS News projects Mitt Romney will win the state of West Virginia, where polls closed at 7:30 p.m., giving him five more electoral votes. That brings his tally of electoral votes to 24, while President Obama is projected to win Vermont, which would give him three electoral votes.
Ohio, with 18 electoral votes, is one of the most competitive states on the map. Mr. Obama won the state by 4.6 percent in 2008. In 2004, President Bush won Ohio by 2.1 percent.
North Carolina, meanwhile, carries 15 electoral votes. Youth and minority voters helped Mr. Obama carry a slim, o.3 percent margin of victory there in 2008. Mr. Bush won North Carolina by 2.9 percent in 2004.
7 p.m. ET: The presidential race is razor thin in the key state of Virginia, where polls are now closed, according to CBS News early exit polling.
As of 7 p.m. ET, polls are closed in a total of six states. Mitt Romney is projected to win Indiana, a red state President Obama won by one point in 2008, as well as Kentucky, giving him 19 electoral votes so far.
Mr. Obama is projected to win one state where the polls have closed, Vermont, for three electoral votes.
Polls have closed in Georgia and South Carolina as well, but results have yet to come in.
The race to 270 electoral votes -- the minimum number needed to win the Electoral College and take the White House -- will come down to a handful of battleground states, including Virginia. In 2008, Mr. Obama won Virginia by seven points, making him the first Democratic presidential candidate to win the state since 1964.
shows Romney leads among men in Virginia, while Mr. Obama leads among women. There are also large divides when it comes to race and age.