Several trends have sped the declining popularity and power of the parties in the United States. Party-run patronage schemes that rewarded supporters with government jobs have long given way to more meritocratic systems. The rise of independent political action committees has given candidates a source of campaign funding — around $4.5bn (£3.17bn) in the last decade – outside the party channels that once dominated access to campaign money. This has made many candidates more entrepreneurial and less beholden to the party bureaucracy.

Thirdly, parties now determine their candidates through primary elections instead of with meetings of party insiders. Just 17 primaries were held in 1968 – today every state has a primary or caucus. This switch to universal primaries has shifted influence from party veterans to more extreme activists, who are more likely than average voters to vote in primaries, says Ian Shapiro, a political scientist at Yale. In 2018, the Democratic National Committee even cut back on the influence of superdelegates, the hundreds of party VIPs who also had votes in selecting candidates. This was to reassure voters that party officials were listening to them, the DNC’s vice-chair said at the time.

In many parts of the United States, partisan gerrymandering has contributed to making candidates less representative of their constituents by creating “safe seats” for both parties. That means that the winners are, in effect, decided in the primaries that pit Democrats against Democrats and Republicans against Republicans. This phenomenon helps explain the 2018 election of Alexandra Ocasio-Cortez, then a 28-year-old democratic socialist who had never before held elected office, says Shapiro. Ocasio-Cortez beat an establishment Democrat in a primary in which less than 12% of voters turned out.

Not everyone agrees that political parties are weaker today than they once were. Today’s extreme polarisation means that much of the public is more strongly attached to their own party, says Rosenblum, and party-led voter suppression or voter mobilisation efforts in fact make party leaders more powerful than ever.

Still, Shapiro and many other experts believe political parties have suffered a major loss in clout, which in turn has been a loss for democracy in general.

“Political parties are the core institution of democratic accountability because parties, not the individuals who support or comprise them, can offer competing visions of the public good,” write Shapiro and his Yale colleague, Frances Rosenbluth, in a 2018 opinion piece. Voters, they argue, have neither the time nor the background to research costs and benefits of policies and weigh their personal interests against what’s best for the majority in the long run.

To show what can go wrong with single-issue voting that lacks party guidance, Shapiro and Rosenbluth point to California’s notorious Proposition 13, a 1978 ballot initiative that sharply restricted increases in property taxes. At first, the measure seemed like a win to many voters. Yet over the years, the new rule also decimated local budgets to the point where California’s per-pupil school spending now ranks near the bottom of a list of the 50 states.

Parties serve many other important roles, including facilitating compromise, says Russell Muirhead, a political scientist at Dartmouth University and Rosenblum’s co-author. As an example, Muirhead points to the US Farm Bill, which the two parties renegotiate roughly every five years. Each time they sit down, “the Democrats want food support for urban people and Republicans want support for farmers, and somehow, they always come to an agreement,” Muirhead says. “The alternative is favouring one side or simply passing nothing at all.”

Perhaps most important, the US’s two main parties have traditionally cooperated in acknowledging their opponents’ legitimacy, as Rosenblum and Muirhead write. Other nations, such as Thailand, Turkey and Germany, have banned political parties that their governments have seen as too destabilising to democracy. American parties’ cooperation has helped keep the peace by reassuring US voters that even if they lose today, they may well win tomorrow. Now, however, this fundamental rule is being broken, say Rosenblum, Muirhead and others, with some party leaders even accusing their opponents of treason.

“In the United States, 140 of the 535 people serving in Congress have a net worth over $2m (£1.4m), 78% are male, 83% are white, and more than 50% were previously lawyers or businesspeople,” he wrote.

Several European nations have already tried alternatives to party-driven democracy. In 2019-20, France held a Citizens’ Convention on Climate, calling on 150 randomly chosen citizens to help devise socially just ways to reduce greenhouse gases. In December 2020, the French President agreed to hold a referendum on one of the convention’s suggestions, the inclusion of climate protection in the national constitution.

And in 2016, the Irish Parliament assembled 99 citizens to deliberate on stubborn issues, including a constitutional ban on abortion. A majority of the assembly proposed that the ban be struck down, after which a national referendum confirmed the result and changed the law – all accomplished without involvement of established political parties.

Despite the limited impact of these efforts to date, Landemore says the tide of public opinion is turning. Just five years ago, colleagues mocked the notion of an “open democracy” at a political science conference, she says, adding: “Five years from now I’m guessing we’ll be completely mainstream.”