“A LIBERAL,” said Robert Frost, an American poet, “is a man too broad-minded to take his own side in a quarrel.” An ad released less than a week before election day by Mark Eves and Betsy Sweet (pictured above), opponents in Maine’s Democratic gubernatorial primary, seemed a paragon of Frostian liberalism. Ms Sweet, who resembles a slightly less caffeinated Elizabeth Warren, urged her supporters to vote for Mr Eves; while Mr Eves asked his supporters to back Ms Sweet. On election day the two gripped and grinned together outside an elementary school in Portland’s lovely West End.

In fact, their alliance was not wet leftism; it was a strategic gambit. On June 12th Maine conducted the first-ever statewide election using ranked-choice voting (RCV), in which voters rank the entire field rather than just voting for a single candidate. Trailing in the polls, Ms Sweet and Mr Eves figured they could boost their chances by campaigning for second-place votes.

RCV has long been a darling of political scientists. But Maine’s experiment should interest anyone frustrated by America’s cripplingly partisan politics. RCV may be unable to force liberals and conservatives to like each other, but it could at least blunt the electoral effects of hyperpartisanship.

RCV is not new. Australia has used it for a century, Malta and Ireland for slightly less. Some Oscar winners are chosen by RCV, as are prizewinners at the World Science Fiction Convention. Several American cities—including Minneapolis, San Francisco, Portland (Maine) and Santa Fe—have recently adopted it, too. In an RCV election, voters rank the field by preference, from first to last (though they can always choose to vote for just one candidate). If one candidate gathers a majority of first-place votes when all votes are in, he wins. If not, the candidate with the smallest number of first-choice votes is eliminated, and his secondary, tertiary and so forth votes are redistributed. That process continues until one candidate eventually has a majority.

How long that takes varies. San Francisco’s mayoral race took place on June 5th but the winner was not confirmed until June 13th. By contrast, three years ago Ethan Strimling won a majority of votes outright in Portland, Maine’s mayoral race. As The Economist went to press, Sean Moody appeared to have won the Republican governor’s race outright, while Janet Mills held a steady lead on the Democratic side.

RCV boosters say it changes campaigns and elections in three laudable ways. First, it encourages voter turnout. A study of 79 elections in 26 American cities found that RCV was associated with a 10% increase in turnout compared with non-RCV primary and run-off elections, and San Francisco’s race had the highest primary turnout in years. Voters turned off by the front-runners have less incentive to stay home. They can give their first-choice vote to their favourite candidate, even if he might be a quixotic choice, while allocating their other choices strategically.

Second, it shifts incentives away from negative campaigning—because candidates are trying not just to turn out their base, but also to win as many second- and third-choice votes as possible—and towards alliance-building, as Mr Eves and Ms Sweet demonstrate. Finally, boosters argue that introducing RCV limits the efficacy, and therefore the amount, of money spent by single-issue campaign groups, because they often finance negative ads.

In theory, RCV elections will more often be won by candidates broadly acceptable to most voters. Kyle Bailey and Cara McCormick, who have led Maine’s RCV campaign, said they have staged dozens of mock RCV beer elections in microbreweries (which abound in Maine: winter here is long, cold and dark) to show voters how the process works. Mr Bailey said the loudest backers would often argue for oyster stout, or some other niche beer style, but the most votes would inevitably accrue to a “middle-of-the-road IPA”—which perhaps had fewer or less ardent fans, but which everyone could drink.

Opponents argue that RCV is too complicated—and indeed, in Maine, people’s enthusiasm for RCV sometimes outstrips their ability to explain it. (Though on election day Maine’s secretary of state, whose office released a detailed video explaining RCV, said he had received no complaints about ballot complexity.) RCV support in the state has split along party lines: Republicans largely opposed it, while the RCV campaign’s watch party offered six types of Kombucha (fermented tea) on tap.

Paul LePage, the abrasive and bombastic outgoing governor, won two elections without a majority, thanks to liberals splitting their vote. Perhaps Maine Republicans doubt their ability to appeal to a majority of voters, and instead must discourage turnout while pandering to their own base? The state party filed an unsuccessful lawsuit in May, tortuously arguing that RCV impinged on their rights of association under the First Amendment.

After Maine’s voters approved RCV by referendum in 2016, Republicans in the legislature narrowly passed a bill blocking its implementation. But backers gathered enough signatures—in a frenzied, dead-of-winter campaign across the state—to pass a “people’s veto” that retained RCV in this election, and asked Maine’s voters on this year’s ballot whether they wanted to use it again. Guardedly optimistic as results filtered in on election night, Ms McCormick vowed that, if Maine voters approved it (and it looks as if they did), she and her colleagues would take their campaign to more states. Get ready to rank, America.