A pioneering electoral reform that passed in Maine last November has hit a snag: The state's top court says it violates the state constitution.

Maine voters last year approved Question 5, a measure changing the way statewide elections would be tabulated. Under the new "ranked choice" system, voters would not simply select one candidate and check a box. Instead they'd be able to rank each candidate in order of preference. If no candidate wins a majority on the first tally, the candidate with the least votes would be tossed from the race. Then the ballots would be recounted, and those who voted for the eliminated candidate would have their votes go to their second choice instead. This would continue until a candidate gets a majority.

Ranked choice voting already occurs in a handful of American cities for local elections. Maine was going to be the first place to implement it for statewide and legislative races.

But the state's Supreme Judicial Court ruled unanimously this week that the Maine constitution forbids it. Under that document, the governor and state-level lawmakers must be selected by earning a plurality of the vote, not a majority.

The court's ruling is advisory, and it doesn't actually strike down the initiative. The purpose is to let lawmakers know that Question 5 is unconstitutional as-is; how legislators deal with that is up to them. Still, if the state does nothing and lets ranked choice voting commence in 2018, there could be legal challenges to the elections' outcomes.

Many Republican leaders in Maine opposed a shift to ranked choice voting. (The state's colorful and controversial Republican Gov. Paul LePage was elected with a plurality.) But a ranked choice system isn't just a threat to the GOP. By essentially eliminating the fear of "throwing your vote away" or bolstering a "spoiler," it could pose a serious challenge to the two-party system's stranglehold. A citizen who isn't satisfied with the Democrat and Republican would be able to pick a third option, then rank one of the major-party nominees higher than the other. If their first choice does poorly and gets knocked out, their vote isn't wasted. Imagine how candidate behavior might change if voters were able to reject the "lesser of two evils" argument.

FairVote, a non-profit group devoted to promoting ranked-choice voting reform, is calling for lawmakers in Maine to update the state's constitution so that Question 5 may be implemented without fear of legal challenges:

Maine voters embraced ranked choice voting because they wanted a stronger voice, more civil campaigns, and to reform our toxic politics. This opinion must not stand in the way of the will of the people. We call on the Maine legislature to uphold the will of the people and support a constitutional amendment to enact [ranked choice voting] for all statewide elections in Maine. Ranked choice voting is also still plainly constitutional for major offices in Maine, including elections for U.S. Senate and U.S. House. Those elections have been affected by split-votes in the past, and will benefit from the use of ranked choice voting going forward.

Independent and third-party voters should keep a close eye on Maine's 2018 election, particularly as the two major parties grow more polarized and perhaps a bit body-slammy. As I wrote in November, ranked choice voting "doesn't necessarily mean an increased likelihood of third-party or independent candidates winning, and that's not how we should grade success. We should look for outcomes like electoral participation, satisfaction with choices, what issues become central to the races, and overall happiness and support for whomever wins."

Bonus link: In December, Reason's Zach Weissmueller interviewed Richard Woodbury of Maine's Committee for Ranked Choice Voting about what such a system would mean for American politics. Listen to that podcast here.