President Obama waited in Chicago as Election Day results became known while Republican rival Mitt Romney watched results in Boston.
So far, no surprises have been found in states projected to break either for the incumbent Democrat or the GOP hopeful.
Logged in Obama's column are Vermont, with three electoral votes; Connecticut, seven electoral votes; District of Columbia, three electoral votes; Illinois, 20 electoral votes; Maryland, 10 electoral votes; Massachusetts, 11 electoral votes, Rhode Island, four electoral votes, and Maine with three of four electoral votes, CNN projected. (Maine can split its electoral vote allocation.)
States on Romney's side of the ledger are Georgia with 16 electoral votes, South Carolina, nine electoral votes; West Virginia, five electoral votes, Oklahoma, seven electoral votes; Indiana, 11 electoral votes; and Kentucky, eight electoral votes, CNN projected.
Lines of voters snaked out of polling places and onto sidewalks in what both U.S. presidential candidates have called an election on the country's future.
Obama shot hoops to shake off the jitters while Romney made a few more campaign appearances.
In a video message sent early Tuesday evening, Obama urged viewers to vote.
"Election Day is almost over. This is it. We won't get another chance tomorrow," he said in the video. "Stop watching this video and go vote."
He also reminded people if they're in line when polls close, they can still vote.
Also on the stump were Vice President Joe Biden and Republican vice presidential nominee Paul Ryan.
In New Hampshire, a battleground state, crowds of after-work voters were packed in polling places and spilling out onto sidewalks and streets, creating safety issues, CNN reported.
In other battleground states, video showed people lined up and waiting to cast their ballots. Various media said they received reports of voters leaving the lines because, among other things, they had to go to work.
In an interview with Washington's WJLA-TV, Obama said he felt "pretty good" about what his campaign has done.
"So far we've run a race that we can be proud of," Obama said, adding he wouldn't have done much else different other than perhaps having "a few more cups of coffee before the first debate," in which he fared poorly.
Romney also told reporters he had no regrets about how he ran his campaign.
Early results from the tiny New Hampshire hamlet of Dixville-Notch reported an even split between Obama and Romney, the first time candidates have tied in that community. The hamlet, which votes at midnight, reported five votes each for the president and his GOP challenger. In 2004, Obama received 15 of the 21 votes cast.
In Hart's Location, N.H., whose population of 41 is nearly four times Dixville Notch's 12, Obama won with 23 votes, Romney received 9 and Libertarian Party nominee Gary Johnson got 1 vote.
As voters lined up, election challenges already were under way.
In Ohio, seen as crucial in deciding the next president, a federal judge rejected claims in a lawsuit filed Monday that raised questions about software used in some of the voting equipment in the state because of fears of viruses or human manipulation. State officials argued the lawsuit by a Columbus State Community College professor was frivolous.
In Philadelphia, Republican officials filed a protest in the Court of Common Pleas, alleging GOP inspectors were blocked from polling places.
In Chicago, the Board of Elections website crashed because so many voters were trying to determine where to vote. Redistricting sent about 20 percent of Cook County voters to new polling sites and at least 539 people showed up at the wrong ones Tuesday. The Chicago Tribune reported the state website, to which the Chicago website redirected queries, also experienced periodic problems.
