WASHINGTON — Donald Trump was elected America’s 45th president in the early hours of this morning, an astonishing victory for a celebrity businessman and political novice who capitalised on voters’ economic anxieties, took advantage of racial tensions and overcame a string of sexual assault allegations on his way to the White House.

His triumph over Hillary Clinton will end eight years of Democratic dominance of the White House and threatens to undo major achievements of President Barack Obama. He’s pledged to act quickly to repeal Obama’s landmark healthcare law, revoke the nuclear agreement with Iran and rewrite important trade deals with other countries, particularly Mexico and Canada.

The Republican blasted through Democrats’ longstanding firewall, carrying Pennsylvania and Wisconsin, states that hadn’t voted for a GOP presidential candidate since the 1980s. He needed to win nearly all of the competitive battleground states, and he did just that, claiming Florida, Ohio, North Carolina and others. In his victory speech in front of his euphoric supporters, Trump said: “Hillary has worked very hard and very hard over a very long period of time and we owe her a major debt of gratitude for her service to this country. Now it is time for America to bind the wounds of division.

“I pledge to every citizen of our land that I will be President for every American. And that is very important to me.

“For those that have chosen not to support me in the past, of which there were a few people, I’m reaching out to you for your guidance and your help so we can work together and unify our great country.”

However, despite the conciliatory tone of his acceptance speech, global stock markets and US stock futures plunged deeply, reflecting investor alarm over what a Trump presidency might mean for the economy and trade.

A New York real estate developer who lives in a sparkling Manhattan high-rise, Trump forged a striking connection with white, working-class Americans who feel left behind in a changing economy and diversifying country. He cast immigration, both from Latin America and the Middle East, as the root of the problems plaguing many Americans and tapped into fears of terrorism emanating at home and abroad.

Trump will take office with Congress expected to be fully under Republican control. GOP Senate candidates fended off Democratic challengers in key states and appeared poised to maintain the majority. Republicans also maintained their grip on the House. Senate control means Trump will have great leeway in appointing Supreme Court justices, which could mean a major change to the right that would last for decades.

Trump upended years of political convention on his way to the White House, levelling harshly personal insults on his rivals, deeming Mexican immigrants rapists and murderers, and vowing to temporarily suspend Muslim immigration to the US.

He never released his tax returns, breaking with decades of campaign tradition, and eschewed the kind of robust data and field efforts that helped Obama win two terms in the White House, relying instead on his large, freewheeling rallies to energise supporters. His campaign was frequently in chaos, and he cycled through three campaign managers this year.

His final campaign manager, Kellyanne Conway, touted the team’s accomplishments as the final results rolled in, writing on Twitter that “rally crowds matter” and “we expanded the map”.

The mood at Clinton’s party grew bleak as the night wore out, with some supporters leaving, others crying and hugging each other. Top campaign aides stopped returning calls and texts, as Clinton and her family hunkered down in a luxury hotel watching the returns.

At 2am, Clinton campaign chairman John Podesta told the crowd to head home for the night. “We’re still counting votes and every vote should count,” he said.

Trump will inherit an anxious nation, deeply divided by economic and educational opportunities, race and culture.

Exit polls underscored the fractures: women nationwide supported Clinton by a double-digit margin, while men were significantly more likely to back Trump. More than half of white voters backed the Republican, while nearly nine in ten blacks and two-thirds of Hispanics voted for the Democrat.

Doug Ratliff, a 67-year-old businessman from Richlands, Virginia, said Trump’s election would be one of the happiest days of his life.

“This county has had no hope,” said Ratliff, who owns strip malls in the area badly beaten by the collapse of the coal industry.

“You have no idea what it would mean for the people if Trump won. They’ll have hope again. Things will change. I know he’s not going to be perfect. But he’s got a heart. And he gives people hope.”

Trump has pledged to usher in a series of sweeping changes to US domestic and foreign policy: repealing Obama’s signature healthcare law, though he has been vague on what he could replace it with; building a wall along the US-Mexico border; and suspending immigration from country’s with terrorism ties. He’s also praised Russian President Vladimir Putin and spoken of building a better relationship with Moscow, worrying some in his own party who fear he’ll go easy on Putin’s provocations.

The Republican Party’s tortured relationship with its nominee was evident right up to the end. Former President George W. Bush and wife Laura Bush declined to back Trump, instead selecting “none of the above” when they voted for president, according to spokesman Freddy Ford.

House Speaker Paul Ryan, a reluctant Trump supporter, called the businessman earlier in the evening to congratulate him, according to a Ryan spokeswoman.

Democrats, as well as some Republicans, expected Trump’s unconventional candidacy would damage down-ballot races and even flip some reliably red states in the presidential race. But Trump held on to Republican territory, including in Georgia and Utah, where Clinton’s campaign confidently invested resources.

Clinton asked voters to keep the White House in her party’s hands for a third straight term. She cast herself as heir to President Barack Obama’s legacy and pledged to make good on his unfinished agenda, including passing immigration legislation, tightening restrictions on guns and tweaking his signature healthcare law.

But she struggled throughout the race with persistent questions about her honesty and trustworthiness.

Those troubles flared anew late in the race, when FBI Director James Comey announced a review of new e-mails from her tenure at the State Department.