IN THE latest instalment in a long-running series, the ghosts of Donald Trump’s past tweets have once again come back to haunt him.

The newly inaugurated US president used Twitter to mock protesters, millions of whom gathered across America and the globe on Saturday, to express their opposition to his leadership.

But Mr Trump had either forgotten or did not care that, just four years ago, he made an unsuccessful attempt to lead his own supporters in protest at Barack Obama’s re-election.

In a tweet on Sunday morning, the president mocked protesters, questioning whether they voted and criticising celebrities for taking part.

Watched protests yesterday but was under the impression that we just had an election! Why didn't these people vote? Celebs hurt cause badly. — Donald J. Trump (@realDonaldTrump) January 22, 2017

Though it did take just two hours, perhaps after some sage advice from staffers about the diplomacy required in his new role, for Mr Trump to issue a more rational tweet, this one recognising the rights of protesters.

Peaceful protests are a hallmark of our democracy. Even if I don't always agree, I recognize the rights of people to express their views. — Donald J. Trump (@realDonaldTrump) January 22, 2017

Four years ago, however, there was no such sensibility to be found on his Twitter account, as the results of the election were revealed.

In a series of tweets, some since deleted, Mr Trump condemned America’s Electoral College system, after incorrectly interpreting Mr Obama to have won the election but not the popular vote.

He urged people to publicly demonstrate.

In what online news site Mashable described at the time as a “melodramatic freak-out”, Mr Trump fired off a string of tweets attacking the very democratic process by which he would himself find himself elected four years later.

The electoral college is a disaster for a democracy. — Donald J. Trump (@realDonaldTrump) November 7, 2012

This election is a total sham and a travesty. We are not a democracy! — Donald J. Trump (@realDonaldTrump) November 7, 2012

Our country is now in serious and unprecedented trouble...like never before. — Donald J. Trump (@realDonaldTrump) November 7, 2012

In the deleted tweets, he said, “The phoney (sic) electoral college made a laughing stock out of our nation,” and he attacked Mr Obama’s re-election, and called for a revolution.

“He lost the popular vote by a lot and won the election. We should have a revolution in this country!”

Four years later, he would sing the praises of the “phony” system, after he lost the popular vote but found himself in the oval office.

In 2012, however, Mr Trump had a public demonstration in his sights.

We can't let this happen. We should march on Washington and stop this travesty. Our nation is totally divided! — Donald J. Trump (@realDonaldTrump) November 7, 2012

Lets fight like hell and stop this great and disgusting injustice! The world is laughing at us. — Donald J. Trump (@realDonaldTrump) November 7, 2012

More than two million people flooded US cities on Saturday as women opposed to Donald Trump led a peaceful, stunning rebuke against the new US president that was echoed in sister protests around the world.

As a sea of demonstrators brought downtown Washington to a standstill, streaming past the White House in a parade of pink “pussyhats,” Mr Trump did not acknowledge the mass protests that marked his first full day in office.

though the US capital does not release crowd counts, organisers of the main protest, the Women’s March on Washington, told AFP they estimated turnout at one million — quadrupling initial expectations — with some 600 sister protests held around the globe.

Mr Trump’s defeated rival Hillary Clinton tweeted her support, while former secretary of state John Kerry was spotted in the crowd — a day after leaving office — with his dog on a pink leash.

Celebrities Scarlett Johansson and Michael Moore were among the speakers, and pop diva Madonna made an impromptu appearance on the Washington protest stage to deliver an expletive-laden indictment of the president.

“Welcome to the revolution of love,” the 58-year-old intoned, wearing her own black pussyhat. “To the rebellion. To our refusal as women to accept this new age of tyranny.”

Mr Trump’s condemnation of the protesters after calling for his own against Mr Obama is, of course, not the first time he has changed his Twitter tune.

Just two weeks after his surprise election last year, he was singing the praises of the “genius” of the electoral college system.

The Electoral College is actually genius in that it brings all states, including the smaller ones, into play. Campaigning is much different! — Donald J. Trump (@realDonaldTrump) November 15, 2016

In the lead-up to last year’s election, he repeatedly tweeted that the voting was “rigged”.