PORTLAND, Maine — The 2020 election in Maine on Tuesday will carry a footnote: It marked the first use of ranked choice voting in a presidential contest in the U.S.

Maine voters first approved ranked voting in federal races in a statewide referendum in 2016. The Legislature later enacted a law to ensure that it’s used in the presidential race.

Republicans sought unsuccessfully to force a “People’s Veto” referendum that would’ve delayed use of the voting system in presidential contest.

There are five candidates on the presidential ballot, including Republican President Donald Trump and Democratic former Vice President Joe Biden. If none of them wins a majority of first-round votes, then there will be additional tabulations in which last-place candidates are eliminated and those supporters’ second-place choices are reallocated to the remaining field.

Ranked voting is sometimes called an “instant runoff.” But there’s nothing instant about Maine’s implementation of the voting system.

If additional tabulations are required, then all the ballots from hundreds of municipalities have to be shipped to Augusta and entered into a computer which completes the additional tabulations.

The voting system is not used for state legislative or governor’s races because of concerns it runs afoul of the Maine Constitution.

Other races include:

SENATE RACE

The Senate contest between incumbent Republican U.S. Sen. Susan Collins and Democratic Maine House Speaker Sara Gideon is the costliest political race in Maine history.

The two candidates and their allies together have spent more than $120 million on television advertising alone.

Collins is battling for a fifth term against a candidate who drew donations for all corners of the country. Democratic support quickly coalesced around Gideon as Collins’ vote for Trump’s Supreme Court nominee Brett Kavanaugh ensured the race would draw national attention and cash.

For all the fundraising, neither candidate had an edge in the polls ahead of Election Day.

2ND DISTRICT

Democratic U.S. Rep. Jared Golden is battling Trump ally Dale Crafts in the vast, rural 2nd Congressional District.

Golden, who narrowly defeated GOP Rep. Bruce Poliquin thanks to ranked voting in 2018, describes himself as a moderate voice for all Mainers. He has pledged to keep supporting small business and traditional rural industries, and to make access to health care a priority.

Crafts, a Republican, is a businessman and former state lawmaker who is counting on Trump’s popularity in the 2nd Congressional District and endorsement carrying him to victory.

1ST DISTRICT

Democratic U.S. Rep. Chellie Pingree is considered a safe bet in her reelection battle against Republican Jay Allen.

Pingree, 65, is seeking a seventh term in a liberal district that has been friendly to her over the years. If reelected, she would be the first person in six decades to be elected to more than six consecutive terms representing the 1st Congressional District.

Allen is a family physician and former Army doctor from the Bristol area who is running on a staunchly conservative platform.

He hopes his campaign will be propelled by voters turning out for Trump at the top of the ticket.

NO REFERENDUMS

A referendum on a proposed power corridor in western Maine wasn’t on the ballot.

Opponents of Central Maine Power’s $1 billion New England Clean Energy Connect that aims to serve as a conduit for Canadian hydropower obtained enough signatures for a statewide referendum. But the Maine Supreme Judicial Court ruled the referendum violated the Maine Constitution because referendums can be used only to nullify legislative actions, not state agency actions.