A teenage member of the electoral college will be the seventh person to break ranks by not voting for Donald Trump, adding to a small but growing pool of so-called "faithless electors".

Washington state member, 19-year-old Levi Guerra, has said she will join the “Hamilton electors”, named after Alexander Hamilton, a renegade group that believes the 538 electors have a moral responsibility to prevent demagogues from entering the White House.

"I promised those that elected me that I might do the whole lot I might to make sure Trump didn’t grow to be our president. To maintain this promise, I consider I need to forged my vote for an alternate Republican," she said at a press conference.

Ms Guerra is one of 12 electors in the state who will have been mandated to vote for Hillary Clinton, who won in their state on 8 November.

Ms Clinton has a lead of at least 2.5 million votes in the popular count but the electoral college system, starting with the Founding Fathers, guarantees a winner takes all system in each state.

The Democrat won 53 per cent of the vote in Washington compared to Mr Trump’s 37 per cent.

Electoral College voting: How the United States decides its president

But instead of voting for Ms Clinton, the teenager plans to cast her vote for a more “moderate” Republican, hoping other party members will follow suit. She has not named which Republican that will be.

Ms Guerra is now the third faithless elector in her state who is demonstrating a protest vote against Mr Trump. They join four electors in Colorado who have vowed to vote in the same way. Art Sisneros from Texas, a Republican elector, said he would also defect as it would “bring dishonour to God” to vote for Mr Trump.

President Trump protests Show all 20 1 /20 President Trump protests President Trump protests Patrons hold a sign as people march by while protesting the election of Republican Donald Trump as the president of the United States in downtown Los Angeles, California Reuters President Trump protests Demonstrators rally following the election of Republican Donald Trump as President of the United States, in Oakland, California Reuters President Trump protests Demonstrators march following the election of Donald Trump as President of the United States Reuters President Trump protests Thousands of protesters rallied across the United States expressing shock and anger over Donald Trump's election, vowing to oppose divisive views they say helped the Republican billionaire win the presidency AFP/Getty Images President Trump protests Demonstrators protest outside the Chicago Theatre in Chicago, Illinois Getty President Trump protests A police officer aims a launcher after demonstrators threw projectiles toward a line of officers during a demonstration in Oakland, California Reuters President Trump protests An officer examines a vandalized police vehicle as demonstrators riot in Oakland, California Reuters President Trump protests Demonstrators take over the Hollywood 101 Freeway just north of Los Angeles City Hall in protest against the election of Republican Donald Trump as President of the United States Reuters President Trump protests A woman holds up a sign reading 'Trump you are an Idiot' as demonstrators gather during a protest against President-elect Donald Trump outside the City Hall building in Los Angeles, California EPA President Trump protests A masked demonstrator gestures toward a police line during a demonstration in Oakland, California Reuters President Trump protests Demonstrators protest against the election of Republican Donald Trump as President of the United States, near the Trump International Hotel & Tower in Las Vegas, Nevada Reuters President Trump protests Musician Lagy Gaga stages a protest against Republican presidential nominee Donald Trump on a sanitation truck outside Trump Tower in New York City Getty President Trump protests A woman yells as she takes part in a protest against President-elect Donald Trump in Seattle's Capitol Hill neighborhood AP President Trump protests A man dressed in red-white-and-blue sits on the curb during a protest against President-elect Donald Trump in Seattle's Capitol Hill neighborhood AP President Trump protests A protester sets off fireworks during a protest against President-elect Donald Trumpin Seattle's Capitol Hill neighborhood AP President Trump protests University of California, Davis students protest on campus in Davis, California, U.S. following the election of Donald Trump as President of the United States Reuters President Trump protests An Oakland police officer checks out damage after a window was broken by protesters at a car dealership in downtown Oakland, Calif AP President Trump protests A protester faces a police line in downtown Oakland, Calif AP President Trump protests President-elect Donald Trumpís victory set off multiple protests AP President Trump protests A fire burns during protests in Oakland, Calif AP

The co-founder of the Hamilton electors in Washington, Bret Chiafolo, faces a $1,000 fine from the state for not following party ranks. He is reportedly considering filing a lawsuit to challenge the fine, arguing that any attempt to force electoral college members to vote against their conscience was unconstitutional.

Electoral College voting: How the United States decides its president

The group acknowledged that their effort to unseat Mr Trump was a long shot, but they felt obligated to take a moral stand.

The last time more than one elector broke ranks in Washington was in 1912, when the Republican vice presidential candidate had died before the vote took place.