Donald Trump officially President-elect after securing Electoral College votes
Donald Trump has surpassed 270 votes in the US Electoral College to formally win the presidency.
The billionaire will become America's 45th president.
An effort by anti-Trump forces to persuade Republican electors to abandon the president-elect came to practically nothing and the process unfolded largely according to its traditions.
Mr Trump's polarising victory on November 8 and the fact Democrat Hillary Clinton had won the national popular vote had stirred an intense lobbying effort, but to no avail.
Even one of Mr Trump's fiercest Republican rivals, Ohio Governor John Kasich, said it was time to get behind the president-elect.
"We want unity, we want love," Mr Kasich said as Ohio's electors voted to back Mr Trump at a statehouse ceremony. Mr Kasich refused to endorse or even vote for Mr Trump in the election.
With several states still voting, Mr Trump had 304 votes and Mrs Clinton had 169. It takes 270 Electoral College votes to win the presidency. Texas put Mr Trump over the top, despite two Republican electors casting protest votes.
Befitting an election filled with acrimony, thousands of protesters converged on state capitols across the country on Monday, urging Republican electors to abandon their party's winning candidate.
More than 200 demonstrators braved freezing temperatures at Pennsylvania's capitol, chanting: "No Trump, no KKK, no fascist USA!"
Mr Trump is at his estate in Palm Beach, Florida, Mar-a-Lago, for Christmas, and is expected to hold more meetings on Monday as he rounds out his administration's top team.
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On Sunday, some of Mr Trump's closest advisers pushed back against Democrats' complaints that Moscow hacked their private emails during the election season in a bid to sow discord among their supporters and sway the election toward Republicans.
"Let's assume it's true," Reince Priebus, Mr Trump's incoming chief of staff, said of Russian interference in the election.
"There's no evidence that shows that the outcome of the election was changed because of a couple dozen John Podesta emails that were out there."
The number of leaked emails by Podesta, Hillary Clinton's campaign manager, was actually closer to tens of thousands.
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Democrats said it was a personal attack and a threat to democracy.
"The emails were weaponised," said Donna Brazile, interim chair of the Democratic National Committee.
"The release of stolen, hacked emails caused a lot of confusion and of course it disrupted our daily campaign life."
CNN severed ties with Brazile, who was a paid commentator for the network, after leaked emails revealed she shared debate questions with Hillary Clinton’s campaign. It is thought she shared at least two questions with Clinton's campaign in advance of CNN-hosted Democratic debates.
Foreign policy experts say part of Russia's calculation was likely a desire for payback for years of US criticism of its own elections and to paint America as a flawed champion of democracy - potentially weakening it on the world stage.
"Where's the evidence?" asked Kellyanne Conway, another close Trump adviser.
On Barack Obama's vow to retaliate against the Russians for hacking, Ms Conway said: "It seems like the president is under pressure from Team Hillary, who can't accept the election results."
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Mr Trump himself weighed in Sunday evening, tweeting: "If my many supporters acted and threatened people like those who lost the election are doing, they would be scorned & called terrible names!"
Mr Trump has previously called the US intelligence agency's finding of Russian involvement "ridiculous".