At least six Democratic electors have signed an agreement to try to block Donald Trump from securing the presidency with 270 Electoral College votes.

While it would be unlikely to convince 37 Republican electors to change their votes - the number needed to erase Trump's lead among the 538 total electors - an unusually large number of 'faithless electors' who refuse to vote for Trump could undermine the institution itself.

In the U.S., presidents are elected by the Electoral College - not by popular vote in which Hillary Clinton is 1.7million votes ahead of Trump. In most states, electors must cast a vote for the winner of their state's popular vote.

But some states like Arizona, Idaho, Michigan and Georgia don't have a rule against electors going rogue, and phone calls from across the country have been pouring in to try to sway them against voting for Trump.

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At least six Democratic electors have signed an agreement to try to block Donald Trump from securing the presidency with 270 Electoral College votes

Votes are still being tallied, but Clinton has more than 1.7million votes ahead of president-elect Donald Trump, even though she only received 232 electoral votes to Trump's 290 (pictured)

Michael Baca is an elector from Colorado trying to block Trump from 270 votes. Even if they fail, a large number of faithless electors could threaten the Electoral College itself

There have been 157 faithless electors over 228 years, 71 of whom changed their votes because a candidate died, according to Fairvote.org.

Even if the electors manage to block Trump from receiving 270 of the 538 votes, the Republican-controlled House of Representatives would likely vote Trump into the White House anyway.

Michael Baca is one member of the Electoral College from Colorado trying to convince others to band together to avoid a Trump presidency when electors cast their votes on December 19.

Baca said: 'I'm a former U.S. Marine and the core values are honor, courage, commitment. I don't believe Donald Trump has that.'

Pictured left, Miriam Vincent, staff attorney at the Office of the Federal Register, responds to emails from citizens inquiring about the electoral college. Right, a protest sign in Pennsylvania

While Baca is a registered Democrat and supported Bernie Sanders, he is considering rallying behind Mitt Romney or John Kasich if that means garnering more support from other electors.

Even if he is unsuccessful in his efforts, Baca said: 'I do think that a byproduct would be a serious look into Electoral College reform.'

Washington state elector, P. Bret Chiafalo, has also joined Baca in the attempt to block a Trump presidency.

Another elector who did not want to be identified said: 'If it gets into the House, the controversy and the uncertainty that would immediately blow up into a political firestorm in the U.S. would cause enough people — my hope is — to look at the whole concept of the Electoral College.'

It remains unclear just how many faithless electors there will be, but political science professor George Edwards III told Politico: 'If you could get eight or 10 Trump electors to vote for someone else...then that would probably get people's attention.'

While a faithless elector's vote is void in Michigan, Mike Banerian disagreed with the idea and told the Detroit News: 'Even if I could, I wouldn't be remotely interested in changing my vote.

HOW DOES THE ELECTORAL COLLEGE WORK? The electoral college is made up of 538 voters - 435 Representatives and 100 Senators, plus three electors for the District of Colombia. A candidate needs to win a majority of 270 electoral college votes to become President. This voters' college are supposed to make their pick based on which candidate receives a majority of votes in their corresponding states. That candidate receives all that state's electoral college votes. It is possible to win the electoral college vote and lose the popular vote - as with George W Bush in 2000. The creators of the Constitution set up the system as a limit on direct democracy - or in Alexander Hamilton's words, as a way of preserving 'the sense of the people' - in other words to avoid a malicious majority forming. An electoral college coup is unlikely, particularly as it's improbable that any Republican elector would vote for Clinton - but protest votes would be possible. That could lead to another Republican taking the presidency. According to a CNN study, around 10 per cent of electors in the past three cycles have considered going against the grain. The electors cast their votes anonymously on the first Monday after the second Wednesday in December (this year, December 19) and are counted in Congress on January 6. The new President is then sworn in on January 20. Advertisement

'The people of Michigan spoke, and it's our job to deliver that message.'

Hillary Clinton's loss is the second time in five elections a Democrat has won the popular vote without securing a majority in the Electoral College.

Votes are still being tallied, but she stands at more than 1.7million votes ahead of president-elect Donald Trump, even though she only received 232 electoral votes to Trump's 290.

Michigan's 16 electoral votes have still not been officially called, although they are expected to go to Trump.

In Arizona, electors have been hit with a barrage of emails and phone calls from unhappy citizens - most of them from out of state.

'It is total harassment,' Robert Graham, an elector and chairman of the state Republican Party, told the Arizona Republic. 'It started about a week ago. Now? 'Bam!' It's hardcore.'

Arizona elector Saron Geise estimates that she has received as many as 8,000 calls and says she has stopped picking up altogether.

It's a similar story just in Idaho, Michigan and Georgia.

California senator Barbara Boxer has already introduced a bill in an attempt to abolish the 'outdated, undemocratic' structure.

The founding fathers created the Electoral College thinking the small group would act as a buffer against the people.