Democratic nominee Hillary Clinton and her Republican rival Donald Trump are locked in a tight fight in swing states as polls close across most of the US most divisive presidential election in recent history.
Early victories for both candidates were long predicted and not particularly significant, but the contest remains too close to call in the battleground states of Ohio, Pennsylvania, North Carolina, Virginia, and Florida.
The winning candidate must secure 270 of the 538 electoral college votes to declare victory.
US television networks have projected that Republicans will retain control of the lower chamber of Congress known as the House of Representatives, where all 435 seats were up for grabs.
New Mexico, Illinois, New York, Rhode Island, Massachusetts, Connecticut, Maryland, New Jersey, Vermont, Delaware and the District of Columbia
Missouri, Montana, Louisiana, Texas, Nebraska, Kansas, South Dakota, North Dakota, Texas, Wyoming, Mississippi, Alabama, South Carolina, Tennessee, Oklahoma, West Virginia, Kentucky, and Indiana
Trump has again hinted that he will refuse to accept election results if he loses.
"We're going to see how things play out," Trump told Fox News on Tuesday, alleging that there had been voting irregularities. "I want to see everything honest."
Trump filed a lawsuit on Tuesday against the Clark County Registrar of Voters in the state of Nevada, alleging that early voting stations were open longer than the designated time.
A Nevada judge denied Trump's request for state voting records on the grounds that the request would potentially put voters at risk of "ridicule and harassment".
Both candidates cast their ballots in New York alongside their spouses.
Clinton started her day by casting her vote in Chappaqua, New York, where she and her husband, former president Bill Clinton, have lived since he left office in 2001. If Clinton wins she will become the nation's first female president.
"I know the responsibility that goes with this," she said as she greeted people waiting at the polling station to see her. "So many people are counting on the outcome of this election and what it means for our country, and I'll do the best I can if I'm fortunate enough to win today."
Al Jazeera's Kimberly Halkett, reporting from New York, said that the Clinton campaign team is "very encouraged by early voting numbers.
"They say there was a historic turnout among the Latinos. They were concerned about African-Americans but even they have come up," she said.
"This is an election we have not seen in a long time where both candidates have very high negatives. Clinton has always had some troubles in the areas of trust. Many believe in the values she represents but do not necessarily love her as a politician."
Trump cast his ballot at a school near his New York home, after which the Republican nominee quipped to reporters that it was a "tough decision" to make his voting choice.
Al Jazeera's Kristen Saloomey, also reporting from New York, said that when Trump arrived at the polling station he was "greeted by jeers and boos".
Clinton has a slim lead in the polls but no one was ruling out a Trump victory. A polling average by tracker site RealClearPolitics gave Clinton a 3.3-percentage point national lead.
"The fact is that he [Trump] has very narrow path to victory. He needs to win some 12 battleground states," Al Jazeera's Saloomey said.
Radically different visions
As a nervous world watched and waited, Americans chose between radically different visions of the future offered by Clinton and Trump.
The 69-year-old former first lady, senator and secretary of state - who is backed by incumbent President Barack Obama - on Monday urged the country to unite and vote for "a hopeful, inclusive, big-hearted America" in her last effort to woo voters.
Trump, meanwhile, pressed his message with voters who feel left behind by globalisation and social change, wrapping up with a flourish on his protectionist slogan of "America first".
Promising to end "years of betrayal," tear up free trade deals, seal the border, halt the drug trade and subject Syrian refugees to "extreme vetting", Trump told his supporters in New Hampshire: "I am with you and I will fight for you and we will win."
|A polling average by tracker site RealClearPolitics gave Clinton a 3.3% national lead over Trump [Reuters]
Trump has repeatedly warned that a "corrupt Washington and media elite" is seeking to rig the race and he said last month that he may not concede defeat if he thinks voting is unfair.
"When he was asked: will he concede the elections, his response was 'We will see'," Saloomey said.
The Al Jazeera correspondent said that Trump has continued with the same theme that has got him this far.
"He has showed his lack of faith in the polls that show him slightly behind Hillary Clinton. He has made some advances in areas that we call Rust Belt here in the US - all the industrial cities and towns where there are lots of working-class voters.
"This has been his strongest area of support," she said.
READ MORE: Understanding Donald Trump's candidacy
Clinton has pushed a more optimistic vision, despite a wobble in the final weeks of her campaign when the FBI reopened an investigation into whether she had put US secrets at risk by using a private email server - only to close the probe again on Sunday.
The email investigation allowed Trump to recover ground lost in a series of recent scandals .
Since announcing his presidential campaign in June 2015, Trump, a billionaire businessman from New York, has consistently alienated minority groups, refused to release his tax returns, and remained seemingly unapologetic for leaked tapes in which he brags about sexually assaulting women.
Voters are also electing candidates for 34 seats in the 100-member Senate and the entire 435-member House of Representatives. Both the House and Senate are now controlled by the Republicans.
With a dominance in Congress, the Republicans frustrated outgoing President Obama by rejecting many of his key legislative agendas.
A Trump victory, along with a Republican Congress, could mean a swift end for Obama's Obamacare health reforms.
To win control of the Senate, Democrats would have to score a net gain of five seats. Republicans currently hold 54 Senate seats to 44 Democratic seats and two independents who align themselves with Democrats.
|Voters are also electing candidates for 34 seats in the 100-member Senate and the entire 435-member House of Representatives [Reuters]
Source: Al Jazeera News