Advocacy group Voter Choice Massachusetts is pushing for the state to implement a ranked-choice voter system, where every voter could list candidates on the ballot as first choice, second choice and so on.

Supporters say such a system, modeled closely after one already in place in Maine, would make every vote matter more and reduce the so-called “spoiler effect.”

Here’s how the system would work:

Ranking candidates

Instead of one circle next to a candidate’s name, there would be multiple, allowing voters to rank each candidate on the ballot in terms of preference.

In Maine’s 2nd Congressional District, for example, there was a Republican incumbent, a Democratic challenger and two independent candidates. Voters who lean toward a third-party candidate could choose one of the independents but select the Democrat as their second or third choice so that, should it come down to a close margin, their votes would play out in the actual decision.

The first round

Perhaps the most important fact about the system is this: ranked-choice voting only comes into effect if, with all first-place votes counted, no candidate reaches a clear majority.

In other words, if any candidate receives more than 50 percent of first-place votes — something that often happens and almost always happens in races with only two candidates — that person automatically wins.

If no one wins outright

Say there are five candidates in a race, and once all first-place ballots have been counted, the top vote-getter stands at 44 percent. That’s where ranked-choice voting comes into effect.

In both Maine’s system and that proposed by Voter Choice Massachusetts, whichever candidate stands at the bottom with the fewest first-place votes is then automatically eliminated. Every ballot that listed that candidate as the top choice then goes to the candidate listed as the second choice, and votes are re-calculated.

If there is still no majority winner by then, the system continues, eliminating the bottom candidate and adding third- and then fourth-place votes until one candidate reached 50 percent plus one vote.

The system has already been deployed: in Maine’s 2nd District race, incumbent U.S. Rep. Bruce Poliquin led after the first round but did not receive 50 percent of votes. Once later rounds were counted, his Democratic challenger Jared Golden had instead cleared 50 percent, making him the victor.

Who to choose

In Maine, ranking each candidate is not necessary. Voters can choose just one candidate, and their ballots will still count.