Senators in Maine have passed a bill that would award the US state’s electoral college votes to the presidential candidate who wins the national popular vote.

The Maine Senate voted 19-16 in favour of joining 15 other states in an agreement aimed at reforming the electoral system.

Under the current electoral college system, voters effectively cast ballots for state electors who in turn select their party's presidential candidate. It gives small states disproportionate influence over who enters the White House.

The mechanism allowed Donald Trump to claim victory over Hillary Clinton in 2016 despite receiving 2.87 million fewer votes nationwide.

Maine’s senators voted to sign up to the National Popular Vote Interstate Compact, which would automatically allocate the state’s electoral college votes to the most popular presidential candidate.

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The bill will now go to the state's House of Representatives, and would also need to be signed off by governor Janet Mills.

The agreement has already been signed by California, Colorado, Connecticut, Delaware, Hawaii, Illinois, Maryland, Massachusetts, New Jersey, New Mexico, New York, Rhode Island, Vermont, Washington state, and the District of Columbia.

But it will only come into effect if states which elect a majority of the 538 members of the electoral college adopt the system. Maine, which elects four electoral college members, would take the current total to 193 out of the 270 needed.

Troy Jackson, the Democrat senator who proposed the bill in Maine, said the current system "gives candidates no reason to campaign or pay attention to voters in states where they are easily ahead or way behind".

He added the majority of Americans supported a system to elect their president on popular vote.

But conservative opponents of the reform have argued it would lead to candidates focusing their campaigns on densely populated cities and neglecting the interests of rural states such as Maine.

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Hillary Clinton won three of Maine's electoral college votes in 2016, with Mr Trump securing the fourth. Maine is one of only two in the US which splits its electoral college votes rather than allocating all to the state's most popular party.

Calls for reform the electoral college system date back decades, but the idea picked up traction in Democrat-leaning states following Mr Trump's election.