Donald Trump's fiercest critics may be dreaming of a last-minute revolt, but the Electoral College, a peculiarly American institution, appears near-certain on Monday to select the 70-year-old real estate mogul as the 45th US president.

Its detractors - and they are many - have denounced an electoral system that flies in the face of the venerated one person, one vote principle, and which encourages presidential candidates to campaign in only a few key states while ignoring whole swaths of the country.

But despite the criticism the method has faced for decades, no reform attempt has ever succeeded.

When American voters cast their ballots on Nov 8, they did not in fact directly elect the next occupant of the White House. Instead, they picked 538 "electors" charged with translating their wishes into reality.

Trump won a clear majority of those electors - 306, with 270 needed for election- despite losing the popular vote to his Democratic rival, Hillary Clinton.

A similar scenario took place in 2000, when George W. Bush became president even though Democrat Al Gore won more popular votes.

However, the gap is far more dramatic in 2016, with Clinton scoring nearly 3 million extra votes over Trump.

This Monday, electors will convene in each of the 50 states, plus the District of Columbia, to officially designate the next president and vice-president.

Following an extraordinarily vitriolic campaign, this step in the electoral process - normally little more than a formality - has been thrust into the spotlight.

Historically, electors only rarely defy the expressed wishes of the majority of voters in their district. And never have the votes of these "faithless electors" changed the outcome of a presidential election.

Still, some Democrats are clinging to the slender hope that a few dozen Republican electors might decide not to vote for their party's populist leader.

Yet, should that happen, it would be up to the House of Representatives to designate the successor to Barack Obama. And Republicans hold a strong majority there.

An online petition calling on electors to reject Trump has collected some 5 million supporters. Hollywood stars including Martin Sheen ("President Bartlet" on the television series West Wing) recently released a video to goad electors to take that step.

"You have the position, the authority and the opportunity to go down in the books as an American hero who changed the course of history," the celebrities say, addressing electors who have been thrust overnight from the shadows into the spotlight.

But these efforts appear to have almost no chance of succeeding: There is no evidence that the requisite 37 Republican electors will decide to abandon Trump. To date, only one of them, Christopher Suprum of Texas, has publicly announced his intention to stage such a revolt.

The future White House chief of staff, Reince Preibus, told Fox News on Sunday that the pressure on the Electoral College not to elect Trump is "about Democrats that can't accept the outcome of the election. It's about delegitimizing the American system."

He added: "We're very confident that everything is going to be very smooth tomorrow."

The final result may not be known on Monday, as states are given several days to report their numbers. The Congress will, in any case, announce the name of the official winner on January 6, two weeks before the next president is to be inaugurated in a solemn and pomp-filled ceremony outside the Capitol.

Asked about it at his final news conference of the year before leaving for a Hawaiian vacation, President Barack Obama acknowledged that the system was "a vestige, it's a carry-over from an earlier vision of how our federal government was going to work," and that it could disadvantage Democrats.