During an interview in late 2016 about the rise of populism, Yascha Mounk, a lecturer at Harvard University who is the author of the new book “The People vs. Democracy,” made an offhand comment that now seems grimly prophetic.

In recent years, he said, Europe’s centre-left and centre-right parties had tended to work together, either unofficially or in a grand coalition, in what was viewed as high-minded and sensible, an important bulwark against the rise of the far right.

But Dr Mounk believed such cooperation ultimately led to instability. Those “ideologically weird” coalitions tend to alienate voters, he said, by implying that there was little real difference between establishment right and left.

And grand-coalition politics, he said, also meant that “the things that the populists have said all along - that everything else in politics is the same and a conspiracy against them, and the only way to change the government is to vote for the populists - become true.”

Dr Mounk worried that this might not only fuel the rise of the far right but could also undermine the stability of European democracy itself.

At the time, his concerns seemed overblown.

But Dr Mounk’s words came readily to mind this past week as the German chancellor, Angela Merkel, announced that her centre-right Christian Democrats had entered into yet another grand coalition with the centre-left Social Democrats.

Though it was nominally a victory for centrist stability, one look at the grim expressions of Ms Merkel and her new cabinet members revealed the truth: Few believe this type of politics is sustainable any more.

A political era is ending in Europe.

What comes next may not be the populist takeover some feared. Rather, it will be a subtler, if no less consequential, form of political hollowing out, with serious consequences for democracy.

In the 2017 election in Germany that set off coalition negotiations, the Christian Democrats and the Social Democrats suffered their worst losses ever in the postwar era, losing more than 100 seats in the Bundestag, the German federal legislature. This has been the story across Europe, as establishment parties plummet in popularity.

Most analysts attributed the German mainstream parties’ losses to voters’ anger at the years of grand-coalition government, which many said had rendered the parties distant and indistinguishable. And so this new coalition, offering more of the same, seems like a rejection of the public will.

It is just the latest sign that Europe may be entering an ominous new political phase.

Agreements between the centre-left and centre-right have long been seen as a fundamental building block of European stability. But now, as such agreements falter, the popularity of mainstream parties is falling fast, with the centre-left’s support collapsing particularly quickly.

In the Netherlands, the far-right Freedom Party’s 2017 election gains grabbed headlines, but mainstream party losses were even bigger.

The Dutch Labour Party, which had been the junior partner in a coalition government before the election, was nearly wiped out, losing 29 of its 38 seats. Its erstwhile coalition partner, the centre-right People’s Party, lost eight seats.

In France, none of the traditional political parties made it past the first round of the presidential election. In legislative elections that followed a few months later, results for the mainstream parties were even worse.

The Socialists, long the largest party of the French center-left, won only 30 seats as President Emmanuel Macron’s brand-new party, En Marche, swept to victory.

Piero Ignazi, a professor of political science at the University of Bologna in Italy, says he believes that as centrist parties have collaborated more closely, voters have come to see them as representing their own elite interests, not those of ordinary citizens.

“People don’t feel represented any longer by the parties,” Prof Ignazi said. “And that sentiment is particularly strong among working-class and low-income people.”

The result, he says, is the rise of what he calls “anti-party sentiment,” which has fueled the extremist parties. “A vote for the far right is a sort of vengeance for being betrayed,” he said.

As voters turn toward anti-establishment parties, polarising away from the centre, that makes it more difficult for parties to cooperate and govern, weakening the system further.

And as politics, and perhaps European societies themselves, become more polarised, that will make it even more difficult for political systems to address major challenges, such as European-Union wide financial strain or the immigration crisis.

Those issues require politicians to balance national or Europe-wide interests against partisan pressures.

In Britain, the Conservative party leadership agreed to the 2016 Brexit referendum in order to stave off defections from the right wing of its base. The results were catastrophically destabilising.

The Labour Party, unlike most of its center-left brethren across Europe, managed to gain in voting share in the most recent election.

But its leader Jeremy Corbyn has himself embraced anti-system politics in many ways, and his allies have clashed with the party mainstream from within.

LOSING THE GATEKEEPERS OF DEMOCRACY

The “essential test” for democratic resilience, Steven Levitsky and Daniel Ziblatt, both political scientists at Harvard University, write in their new book “How Democracies Die(em),” is whether political leaders, and especially political parties, will work together to prevent extremists from gaining power(em).

“Political parties are democracy’s gatekeepers,” they write. “Although mass responses to extremist appeals matter, what matters more is whether political elites, and especially parties, serve as filters.”

And so to protect democracy, parties and other political elites need to keep would-be authoritarians off ballots at election time, root out extremists within their own party’s ranks, refuse alliances with anti-democratic candidates or parties and work to isolate extremists rather than legitimising them.

When that does not happen, they warn, countries risk following in the footsteps of Venezuela, Hungary, Turkey and other nations where elected leaders have chipped away at democracy from within.

But that kind of gatekeeping requires that parties have the strength to enforce discipline within their own ranks and the popularity to maintain voter good will. And as Europe’s mainstream parties crumble, their gatekeeping capacity has, too.

Worrying about the stability of some of the world’s oldest and wealthiest democracies can seem like paranoia. But in an article in Foreign Affairs, Andrea Kendall-Taylor, a senior associate at the Center for Strategic and International Studies, and Erica Frantz, a professor at Michigan State University, warn that citizens in Europe “should hesitate before assuming that they are invulnerable to a populist-driven backslide.”

Europe, they write, is experiencing many of the factors that have led other established democracies to erode: rising populism, social polarisation, weakening institutions, economic insecurity and public distrust of government.

That does not mean Western Europe will turn into Venezuela, but its cherished democracies could grow less effective and more prone to extremism and demagoguery.

The incremental steps of democratic backsliding, they wrote, can mean that “there is no single moment that triggers widespread resistance or creates a focal point around which an opposition can coalesce.”

But, they warn, “if left untamed, they will lead to grave consequences for global democracy.” THE NEW YORK TIMES

ABOUT THE AUTHOR:

Amanda Taub is a writer for The New York Times Interpreter, which explores the ideas and context behind major world events.