In 1997, the Supreme Court heard arguments in Timmons v. Twin Cities Area New Party, on whether states could ban electoral “fusion,” the voting system that allows two or more parties to nominate the same candidate. Defending the ban, the State of Minnesota argued, without evidence, that the fusion system would confuse voters. Minnesota’s lawyer dodged a question on how New York had used the fusion system for more than a century without any confusion, leading Justice Ruth Bader Ginsburg to gently mock Minnesota’s lawyer: “New Yorkers are smarter, I think. That’s probably the answer.”

The advocates of fusion voting lost that fight. Conservative Chief Justice Rehnquist wrote the majority opinion, ruling that Minnesota’s interest in a stable two-party system allowed it to limit the associational rights of minor parties and their supporters.

Today, fusion voting is back in the news. The New York State Democratic Party just passed a resolution calling for its elimination, backed by Governor Cuomo’s newly appointed state-party chairman. The resolution does not bring credit to its author: It says nothing about why fusion exists, what its role was historically, or why it was made illegal in most, but not all, states.

Fusion is a response to the winner-take-all electoral system. It solves the “wasted vote” or “spoiler” dilemmas that otherwise plague third parties, and allows citizens who don’t fit neatly into the Democratic or Republican boxes to nevertheless participate constructively in politics.

And it is important to remember that third parties have played a critical role in American history. Many of our strides towards “a more perfect union”—including the abolition of slavery, the eight-hour day, unemployment insurance, women’s suffrage, Social Security, child-labor laws—began as fringe ideas of third-party activists. They told the truth before the major parties wanted to hear it, and their ideas were eventually adopted by those who initially rejected them.

Today, only eight states allow fusion candidacies, but it was once legal in all states. Abraham Lincoln won reelection in 1864 as the candidate of the Republicans and the “War Democrats,” the fraction of the Democratic Party that wanted to pursue the Civil War until the Confederacy was defeated. In 1872, Horace Greeley ran for president as the fusion candidate of the Liberal Republican Party and the Democrats.

But it was the Populists, or People’s Party, that most proved the potency of fusion in giving voice to the marginalized. During the 1880s and 1890s, the Populists mobilized hard-pressed farmers on the Great Plains, out West, and in the Deep South to challenge the “money power” exercised by the Eastern banks, railroads, and farm-machinery manufacturers. Tactically, fusion gave the Populists a way to hold onto their identity and mobilize their supporters, but also to forge majoritarian alliances. Perhaps the most famous of those alliances was with the Knights of Labor, creating a “farmer-worker” alliance that alarmed the capitalist class in several states.

In the Midwest and West, Populists united with Democrats to challenge imperious business Republicans. In the South, Populists sided with egalitarian Republicans against Jim Crow Democrats. This tactical flexibility was joined to visionary policy ambitions. A generation before such measures became law, the Populists called for the secret ballot, the direct election of senators, the graduated income tax, banking regulation, trust busting, and sweeping labor-law reform . They elected governors, members of Congress, state legislators, and thousands of local officials all across the country. In 1896, at the peak of the Populists’ power, William Jennings Bryan ran for president of the United States as the fusion nominee of both the Populist and Democratic parties.

Populist success with fusion politics alarmed the powers-that-be, and when McKinley defeated Bryan, triumphalist Republicans were determined to change the rules in their favor. State by state, they worked to make fusion illegal as a way to prevent the farmer-worker alliance that it made possible. “We can whip them single-handed,” said one legislator during a debate in the Michigan state house, “but don’t intend to fight all creation!” Like vote suppressors of our own era, politicians are well aware that changing the rules of the game is a powerful way to keep control. It took about 20 years, but by World War 1 most states had eliminated fusion voting and, in so doing, weakened the political influence of dissenters.

Fusion voting endured in but a few states, most famously in New York. During the 1930s and ’40s, the American Labor Party, which for a time enjoyed the support of most of the city’s powerful trade-union movement, engaged in fusion campaigns. FDR was happy to win the endorsement of the ALP, as were other candidates who supported New Deal policies. Fiorello LaGuardia won his race for NYC mayor in 1937 with 1.35 million votes, of which 483,000 came on the ALP line.

In the past 20 years, the Working Families Party has emerged as a lively party presence in more than 15 states. In New York, the WFP has converted its electoral muscle into a solid roster of policy gains: the minimum wage, repeal of the Rockefeller Drug Laws, a substantial “millionaire’s tax,” and paid sick leave, to name but a few accomplishments in which it played a leading role. And it has made the right enemies: the real-estate lobby, school privatizers, Wall Street, and the rogue Democrats who flipped control of the state Senate to the Republicans in 2012.

One might reasonably ask why this is happening now, nearly a hundred years after the last spasm of anti-fusion legislation. Last November, the New York WFP and progressive-minded Democrats joined forces to run the electoral table. Fifteen new state Senators, all running as fusion D-WF candidates, swept the Republicans (and their Democratic allies) into well-earned oblivion. New, progressive leadership has emerged in the Senate, and energetic legislators in both legislative chambers are passing laws that corporate lobbyists can no longer bottle up. Some of those frustrated lobbyists, and even some high-ranking Democrats, might prefer to return to the coalition between the Republicans and rogue Democrats. But they can’t, and in their frustration at the rise of progressivism, they are taking aim instead at the visible targets of the fusion system and the Working Families Party.

New Yorkers are no smarter than Minnesotans, but they do have a better voting system. Their legislators ought to think twice before limiting democracy at the behest of powerful economic and political forces.