The long and contentious race for the White House between Democrat Hillary Clinton and Republican Donald Trump hurtled toward its conclusion on Tuesday as millions of Americans cast ballots, with only hours left to vote.
Clinton led Trump, 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 her a 90 percent chance of defeating Trump and becoming the first U.S. woman president.
In yet another twist to the race, Trump on Tuesday again raised the possibility of not accepting the election's outcome, saying he had seen reports of voting irregularities. He gave few details and Reuters could not immediately verify the existence of such problems.
The campaign focused on the character of the candidates: Clinton, 69, a former U.S. secretary of state, and Trump, 70, a New York businessman. They often accused each other of being fundamentally unfit to lead the United States as it faces challenges such as an arduous economic recovery, Islamist militants and the rise of China.
Financial markets, betting exchanges and online trading platforms largely predicted a Clinton win, although Trump's team says he can pull off an upset victory like the June "Brexit" vote to pull Britain out of the European Union.
Trump's candidacy embodied an attack on America's political establishment. Clinton represented safeguarding the political order.
A Clinton presidency would likely provide continuity from fellow Democrat Barack Obama's eight years in the White House, although if Republicans retain control of at least one chamber in Congress more years of political gridlock in Washington could ensue.
A win for Trump could shake some of the basic building blocks of American foreign policy, such as the NATO alliance and free trade, and reverse some of Obama's domestic achievements such as his 2010 healthcare law.
Voting ends in some states at 7 p.m. Eastern Time (0000 GMT on Wednesday), with the first meaningful results due about an hour later. U.S. television networks called the winner of the 2008 and 2012 presidential elections at 11 p.m. (0400 GMT) or shortly after.
Victory in U.S. 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.
'NOT GOOD CANDIDATES'
Majorities of voters in opinion polls viewed both candidates unfavorably after a marathon campaign that began in early 2015.
"They're both not good candidates, but I'd rather vote for 'worse' than 'worser,'" said Estefani Rico, 20, a first-time voter who cast her ballot for Clinton at a library in Miami. "It's nerve racking that in my first time being able to vote I get the worst candidates ever," she said.
Mary Wheeler, 94, held her nose when asked which candidate she was supporting as she stood in line to vote at the Coliseum ballroom in St. Petersburg, Florida, an important battleground state.
"I always vote Republican, so I guess I'll do that," Wheeler said. "He can make a fool of himself but I think he may be able to straighten things out a little bit," she said of Trump.
Voting appeared to go smoothly despite allegations in recent weeks from Trump that the electoral system was rigged against him. He told Fox News on Tuesday he had seen reports of voting irregularities.
Asked if believed the election would not be over on Tuesday night, Trump said: "I'm not saying that. I have to look at what's happening. There are reports that when people vote for Republicans, the entire ticket switches over to Democrats. You've seen that. It's happening at various places."
Local media in Pennsylvania reported that voters in several counties in the pivotal state had reported that touch-screen voting machines had not been recording their ballots correctly.
Republicans in Pennsylvania also complained that some of their authorized poll watchers were denied access to polling sites in Philadelphia, local media said.
The Pennsylvania secretary of state's office did not immediately respond to a request for comment.
Trump also sued the registrar of voters in Nevada's Clark County over a polling place in Las Vegas that remained open on Friday during an early-voting period to accommodate people, many of them Hispanic, who were lined up to cast ballots.
A Nevada judge on Tuesday rejected Trump's request for records from the polling site. At a court hearing, a county attorney said election officials already preserve records.
Trump and Clinton are seeking to succeed Democrat Obama, who served two four-year terms in the White House and is barred by the U.S. Constitution from seeking another term.
Clinton spent eight years in the White House as U.S. first lady, the wife of President Bill Clinton, from 1993 to 2001 before serving as a senator and as Obama's secretary of state. She also ran for president in 2008, but lost to Obama for the Democratic nomination.
Trump has vowed to crack down on illegal immigration and end trade deals he says are harming U.S. workers.
Trump seized the spotlight time and again during the campaign with provocative comments about Muslims and women, attacks against the Republican establishment and bellicose promises to build a wall along the U.S. southern border with Mexico to stem illegal immigration.
The Dow Jones Industrial Average index ended up 0.4 percent as investors bet on a win for Clinton, who Wall Street sees as more likely to ensure financial and political stability. Mexico's peso hit a two-month high on Tuesday on the expectation of a loss for Trump, who has vowed to rip up a trade deal with Mexico.
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 Clinton would win. Online political stock market PredictIt put her chances on Tuesday of capturing the White House at 80 percent.
Trump advisers say the level of his support is not apparent in opinion polls and point out that the real estate developer has been closing the gap with Clinton in surveys in recent weeks.
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 favoring Clinton to being too close to call, according to opinion polls.
Democrats also are seeking to break the Republican lock on control of the U.S. Congress.
A strong turnout of voters for Clinton could jeopardize 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 are being contested. The House is expected to remain in Republican hands.
Trump reveled in the drama of the negative presidential campaign but the spotlight was not always kind to him. 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. It was only two days before the election that FBI Director James Comey reiterated that she would not face criminal charges.
Trump's vice presidential running mate is Mike Pence, the governor of Indiana. Clinton's running mate is U.S. Senator Tim Kaine of Virginia.