Americans pick between Hillary Clinton and Donald Trump after nasty campaign

Democrat Hillary Clinton held a narrow lead in opinion polls over Republican Donald Trump as millions of Americans have turned out to vote for the next president after one of the most negative campaigns in US history.

In a battle that focused on the character of the candidates, Clinton, 69, a former secretary of state, senator and first lady, and Trump, 70, a New York businessman and former reality TV star, made their final, fervent appeals to supporters late on Monday to turn out the vote.

Clinton led Trump, by 44 percent to 39 percent, in the last Reuters/Ipsos national tracking poll before Election Day.

A Reuters/Ipsos States of the Nation poll gave Clinton a 90 percent chance of defeating Trump and said she was on track to win 303 electoral college votes out of 270 needed.

World financial markets were closely watching the outcome of election, with stocks up slightly on cautious expectations of a Clinton win. The dollar and bond yields slipped, while gold inched up. US stocks had soared on Monday as investors bet on Clinton, seen as the candidate more likely to maintain the status quo.

Polls begin to close at 7pm Eastern Time (0000 GMT on Wednesday), with the first meaningful results due about an hour later. US television networks called the winner of the 2008 and 2012 presidential elections at 11pm (0400 GMT) or shortly after.

Clinton cast her ballot at an elementary school near her home in Chappaqua, New York early on Tuesday morning.

"It is the most humbling feeling. I know how much responsibility goes with this. So many people are counting on the outcome of this election, what it means for our country. And I'll do the very best I can if I'm fortunate enough to win today," Clinton said.

Trump, who planned to vote later in Manhattan, began Election Day with a call to the "Fox & Friends" morning news show.

"It's been a beautiful process. The people of this country are incredible," Trump said of the election. However, he added, "If I don't win, I will consider it a tremendous waste of time, energy and money."

More than 40 million voters cast ballots before Election Day in early voting around the country.

First woman president?

Trump and Clinton were seeking to become the 45th president of the United States and the successor to Democrat Barack Obama, who served two four-year terms in the White House and is barred by the US Constitution from seeking another term.

People wait to vote in the US presidential election at Grace Episcopal Church in The Plains, Virginia, US, Nov 8, 2016. Reuters

Clinton is aiming to become the first US woman president after spending eight years in the White House as first lady from 1993 to 2001 before serving as a US senator from New York and as Obama's secretary of state.

Trump was expected to draw support heavily from white voters without college degrees. Clinton was likely to draw support from college-educated voters and Hispanic and black voters.

Major bookmakers and online exchanges were confident she would win. Online political stock market PredictIt put her chances on Tuesday of capturing the White House at 80 percent, down 2 percentage points from Monday.

Trump advisers say the level of his support is not apparent in opinion polls and that they believe the real estate developer is in position for an upset victory along the lines of the "Brexit" vote in June to pull Britain from the European Union.

"We have seen enormous momentum," Trump deputy campaign manager Dave Bossie said.

Clinton has vowed to largely continue the policies of Obama and to overcome income inequality among Americans, with an unremitting divide between the rich and poor.

Trump, launching his first bid for elected office after decades as a public figure, has positioned himself as an agent of change and has vowed to crack down on illegal immigration and end trade deals he says are harming US workers.

Majorities of voters in opinion polls have viewed both candidates unfavorably.

Victory in US presidential elections is earned not by the popular vote, but by an Electoral College system that awards the White House on the basis of state-by-state wins, meaning a handful of states where the race is close assume an outsized importance.

An early indicator of who might prevail could come in North Carolina and Florida, two must-win states for Trump that were the subject of frantic last-minute efforts by both candidates.

Races in both those states were shifting from favouring Clinton to being too close to call, according to opinion polls.

Democrats also are seeking to break the Republican lock on control of the US Congress.

A strong turnout of voters for Clinton could jeopardise Republican control of the Senate, as voters choose 34 senators of the 100-member chamber on Tuesday. Democrats needed a net gain of five seats to win control. All 435 seats in the House of Representatives were being contested. The House was expected to remain in Republican hands.

Negative campaign

The marathon US election campaign has been one of the most negative in American history, with each candidate accusing the other of lacking the character and judgment to be president.

Trump revelled in the drama and seized the spotlight time and again with provocative comments about Muslims and women, attacks against the Republican establishment and bellicose appeals to build a wall along the US southern border with Mexico to stem illegal immigration.

He said if elected he would seek to prosecute Clinton over her use of a private email server as secretary of state, and led his supporters in chants of "lock her up."

But the spotlight was not always kind to Trump. The release in October of a 2005 video in which he boasted about groping women damaged his campaign and left him on the defensive for critical weeks.

Clinton, with a long reputation for secrecy, sustained damaging blows from her handling of classified information as the country's top diplomat.

Voters cast their votes during the US presidential election in Medina, Ohio, US November 8, 2016. Reuters

FBI Director James Comey shook up the race and slowed Clinton's momentum with an Oct. 28 announcement the agency was reviewing newly discovered emails perhaps related to her email practices.

But on Sunday, two days before the election, Comey told Congress investigators had found no reason to change their July finding that there was no criminal wrongdoing in Clinton's use of the server.

The final week of campaigning was a grinding series of get-out-the-vote rallies across battleground states where the election is likely to be decided.

"We choose to believe in a hopeful, inclusive, big-hearted America," Clinton said in Philadelphia before a crowd on Monday of 33,000, the largest of her campaign.

She was joined by Obama, first lady Michelle Obama, and Clinton's husband, former President Bill Clinton, along with singers Jon Bon Jovi and Bruce Springsteen.

She later made another star-studded appeal in Raleigh, North Carolina, flanked again by Bon Jovi and by singer Lady Gaga in a midnight rally.

At an evening rally in Manchester, New Hampshire, Trump brought much of his family and running mate Mike Pence, the governor of Indiana, on stage. The raucous event in the state that gave Trump his first party primary victory featured a fog machine and red-white-and-blue lasers.

Later, Trump visited the traditionally Democratic state of Michigan, where he framed his candidacy as a historic choice for blue-collar voters he hopes will send him to the White House.

"Today is our Independence Day," Trump said in Grand Rapids. "Today the American working class is going to strike back, finally."