Such practice has been very rare in modern times, with only 157 faithless electors since the establishment of the Electoral College institute, while the record was set in 1836 when 23 electors supported a different candidate from those chosen by their state.
Below is a state-by-state list of when each state's Electoral College meeting takes place - much of this information has been gathered from the National Association of Secretaries of State. Many of the Republicans casting ballots said they were inundated with calls and emails urging them to switch their votes.
A day after all election results in all states were finally certified - and the final vote shows that Donald Trump lost the popular vote to Hillary Clinton by almost 3 million votes - the president-elect is again on the defensive.
"It would be improper to suggest that electors ought not to vote their conscience, otherwise there's no goal in having an Electoral College", says North Central College Professor Stephen Caliendo. But four Washington electors made history Monday when they broke ranks and voted for alternative candidates for president and vice president.
"I would actually be surprised at this point if they did", he said.
While the Electoral College is normally a mundane process, it hasn't been so in this highly charged election year. Under some state laws, those electors could be fined, disqualified or replaced.
On election day, voters technically elect members of the electoral college to decide on their behalf, rather than voting for the candidates themselves. "We haven't won this state for the Republicans in 32 years and I'm really excited to come back to Madison and vote for Mr. Trump".
The state's Democratic electors on Monday signed a certificate that will be delivered to Congress for the final certification of election results in January.
Dec 24 2016 Deadly Explosion Rips Through Fireworks Market Near Mexico City
However, a firefighter told El País that market vendors still didn't always prevent people from trying out the wicks on fireworks. Hundreds of stalls in the same market were destroyed in another explosion in 2005 , and again after a similar fire in 2006.
Dec 22 2016 Van explodes at Canberra's Australian Christian Lobby
The driver's identity and condition are not known. "Prayers appreciated", he tweeted, as reported by the Telegraph . No one inside the building is thought to be injured but the driver is reportedly receiving medical attention.
Dec 21 2016 China returns seized U.S. drone
The admiral said he plans to expand the use of ocean gliders and accelerate the development and deployment of newer systems. If China, or any other nation, starts illegally interdicting U.S. commerce through those waters, only then should the U.S.
Dec 20 2016 Creepy Ghost Shark Finally Caught on Camera
The pointy-nose blue chimaera showcased in recently released video , has been termed as the first of its kind, by scientists. Imagine trying to understand species distribution in Lake Michigan and you sample the lake using a Dixie cup.
Dec 18 2016 First pics of Meghan Markle and Prince Harry emerge
And then, regarding their choice of date: "As an actress Meghan loves the theatre so this was an obvious date to go on". Store employee Ollie Wilkinson told UsMagazine.com, "I gave them a bunch of mistletoe".
Dec 18 2016 BA cabin crew strike
More than half of Virgin Atlantic's about 900 pilots are represented by the Professional Pilots' Union (PPU). Their union, the PPU, said 88 per cent of its members voted in favour on a turnout of 80 per cent.