When voters in Maine go to the polls next month, they’ll not only be casting votes in the presidential and congressional contests. They’ll also be voting on how they vote.

A measure on the Nov. 8 ballot called Question 5 will ask voters whether the state should adopt ranked-choice voting (RCV) in state elections.

Under RCV, voters rank-order up to five candidates. When the votes are counted, if no candidate is listed as the first choice by a majority of voters, the candidate with the fewest first-place votes is eliminated. If a voter’s first choice is dropped, their votes are then assigned to their second-choice candidate for the next round of counting. This process repeats until one candidate receives a majority.

Reformers hope RCV will deal with “spoiler” candidates who take votes away from major-party nominees, producing winners with less than a majority. But this has been an issue in Maine since 2001, and four governors in a row have been elected with less than 50 percent. So why the momentum for a change now?

The answer is partisan politics.

Democrats in the state have rallied to the reformers’ cause because they hope it will help them win. Up until 2014, it wasn’t clear whether changes to the voting rules would have benefited the party. But that year, when Republican Paul LePage won with 48 percent of the vote, a different voting system might have given the Democrats the governor’s office. Two candidates split the Democratic vote, an outcome that could have been avoided under RCV.

While it might seem odd that the political establishment is championing electoral reform — we often think of reform as the province of activists and good government groups — what’s happening in Maine is consistent with historical patterns. Changes to voting laws often are driven by interests of political parties.

In my forthcoming research, I look at changes to voting rules in cities across the United States. During the 20th century, 24 cities used some type of system similar to what’s being considered in Maine. In at least 17 of these cases, reformers joined with a political party that was looking for a way back to political power.

Consider Worcester, Mass. In 1947, a faction of Democrats was disgruntled with the sitting Democratic administration, which they viewed as slow in providing municipal services. This faction proposed RCV in an effort to boot the incumbents out of city hall.

To win majority support for the change, however, these “good government” Democrats needed help from Republicans. Republicans were willing to join forces because they believed it would help them gain control of the city government.

When the voting was done, RCV passed, largely because of help from votes from Republican parts of the city. And in the next election, conducted under RCV rules, the Republican Party won control of city council.

Contrast the story of Worcester with Waterbury, Conn., a similar city that voted down RCV in 1939. Republicans wanted to oust a Democratic administration, which had controlled city government since 1922. Indictments on corruption charges in 1938 threatened to split the Democratic Party, a division that Republicans saw as a chance woo some Democrats to the side of RCV.

But in contrast to what happened in Worcester, the Democratic vote for RCV never materialized, largely because the leader of the insurgent Democrats decided at the last minute to oppose the change. RCV lost because reformers couldn’t persuade the Democrats to get on board, and Waterbury went 10 more years without a Republican administration.

These historical cases suggest that RCV in Maine is likely to succeed or fail based Democratic support. If the reformers win, it will be thanks to Democrats acting in their partisan interest. And if RCV wins and Maine starts electing Democratic governors, Democrats will have reformers to thank.

Jack Santucci is a PhD candidate in government at Georgetown University.