LONDON » Sixty years ago, the two main British political parties, the Conservatives and Labour, took 96 percent of the vote in a clearly defined two-party system. Today, as Britain undergoes a bitter campaign before the May 7 election, the two parties are expected to split less than two-thirds of the vote.

The result is likely to be a weak minority government or another coalition, the second in a row. Britain now has at least six parties that matter, including the Scottish National Party, the English nationalist, anti-immigration U.K. Independence Party and the Greens. To many Britons, it all feels a little too European.

But the fragmentation of traditional party voting is increasing all over Europe, too. Fueled by the last recession and enabled by social media, issue-oriented or protest parties have cropped up everywhere in response to the failure of governments to deliver economic growth and security. The days of a "broad church" party and single-party rule are fading.

At the same time, turnout in national elections has been falling since the 1970s in most Western countries, raising new questions about the health of democracy as multinational corporations and institutions like the European Union, the European Central Bank and the International Monetary Fund influence national decisions.

As expressions of increasingly fractured electorates and the decline of traditional parties, coalitions can produce unity and policy compromises. But they may also produce more homogeneity and gridlock, depriving voters of real choices.

Where coalitions effectively dissolve the differences between the parties that share power, analysts said, they can leave many voters with stronger ideological views feeling frustrated and looking for alternatives.

In Germany, Chancellor Angela Merkel’s third term — like her first — has been a "grand coalition" of the two main and normally opposed parties, her center-right Christian Democrat bloc and the left-leaning Social Democrats. The Free Democrats, her partners in her second term, have all but collapsed. The Greens and the Left Party take votes away from the Social Democrats, while an anti-euro party, the Alternative for Germany, is gaining supporters and an anti-immigrant, anti-Islamist movement, Pegida, is making waves in the east.

Greece is now governed by Syriza, a left-wing protest party, and Spanish politics are being roiled by the emergence of a similar party called Podemos and a copycat on the center-right called Ciudadanos. In Italy, the traditional parties have essentially fallen apart, leaving the field to the Democrats of Prime Minister Matteo Renzi, the regional, euroskeptic Northern League of the young Matteo Salvini and a fading, half-comic opposition, Beppe Grillo’s Five Star Movement.

In France, the governing Socialists and the deeply divided center-right opposition, the Union for a Popular Movement, are being pressed hard from the far left by Jean-Luc Mélenchon and especially hard from the far right by Marine Le Pen and the National Front, which is taking protest votes from both traditional groupings.

Politicians are often seen as beholden to special interests and subject to scandal, a British commentator, Philip Coggan, wrote in his book, "The Last Vote: The Threats to Western Democracy." But the blended soup of coalitions also creates problems.

"Many people also have the feeling that, in practice, there is little difference between the main parties; that, however citizens vote, policies will not change," he wrote. "Like the creatures at the end of George Orwell’s ‘Animal Farm’ gazing at the oppressive humans and the supposedly sympathetic pigs, the voters can no longer tell the difference."

The British Liberal Democrats, for instance, were traditionally the protest vote of the middle classes. But they have lost support by going into coalition with the Conservatives and breaking key promises, like abolishing tuition fees.

In the recent British past, "people angry with the government turned to Labour," said Mark Leonard, director of the European Council on Foreign Relations. "But Labour is now part of the permanent political establishment, without an insurgent voice. It’s why UKIP and others capture the space of being against the status quo."

There are more floating voters, he said. And with the end of the Cold War, "it makes it seem that politics don’t matter as much, and the choices don’t seem as stark."

The number of people voting for mainstream political parties now is dropping in almost all Western European countries. So the mainstream parties look for wedge issues to improve their hard-core support.

Klaus Schueler, the political director for the governing Christian Democrats in Germany, said, "We’ve had a relatively stable political system with a relatively stable political market, and those good old days are gone."

There is also a steady decline in party membership. In Britain, there are only about 495,000 members of the three main British parties, some 0.8 percent of the electorate, down from 3.8 percent in 1983. By contrast, the National Trust has more than 4 million members.

Part of the reason for the decline is socialism’s success, in the last century, in winning key protections for the working class, from trade unions to pensions and national health care, that are hard to finance in an aging population. But the right, which used to represent the landed and corporate rich and those who felt affinity to them, has suffered its own decline.

"Parties of the left, which used to be anchored in the working class, in the trade union movement and factories, are now increasingly dominated by public-sector employees and creative industries like the media," Leonard said. "Parties of the right, which used to stand for the aspirational classes, are now more elitist and metrosexual. The countryside is disgusted by the metrosexual cosmopolitanism of the conservatives and the workers are disgusted by the new left."

Charles Grant, director of the Center for European Reform, emphasizes the failure of the European center-left to keep its promise "to create growth and redistribute it to make a fairer society." With the decline of the manufacturing sector and weaker unions, the left has been forced to buy into the orthodoxy of market economics, which "means their core support has been hollowed out here," he said, as in France, Germany and Sweden.

"The center-left seems intellectually dead," Grant said, little different from the center-right. "So you see alternatives on the far left like Die Linke, Podemos and Syriza," he said.

Meanwhile on the right, he said, politicians and elites are increasingly unpopular, blamed for the 2008 economic crash, the euro crisis, stagnant growth, austerity and bailing out bankers.

The combination of low economic growth, high debt, surging migration and increasing anti-Muslim sentiment provoked by terrorism has put the European Union itself is under great strain, he said. There is a strong anti-austerity feeling on the left and a strong anti-immigration feeling on the right — and neither issue can be easily managed by national governments or coalitions.

In the West, after the Cold War, "we no longer have common ideologies that bind us together," said Gianni Riotta, an Italian who teaches at Princeton. "We used to long for a post-ideological world, and now we have one."

Thomas Stehling runs the British office and now the Spanish office of the Konrad-Adenauer-Stiftung, a political foundation associated with the German Christian Democrats. "It’s more difficult to identify the glue that holds us together in Europe," he said. "Skepticism about Europe feeds a nationalism we haven’t known for many years."

At the same time, he said, "traditional political parties are losing support and the center looks fragmented, manifestoes are less trusted and so personalities are more important for success and failure. But can we attract the right people, or do we get the people we deserve?"

Steven Erlanger, New York Times

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