From the New York Times:

By ALAN COWELL and JAMES KANTER MAY 26, 2014

LONDON — Members of the European political elite expressed alarm on Monday over the strong showing in European Parliament elections by nationalist and anti-immigrant parties skeptical about European integration, a development described by the French prime minister as an “earthquake.”

In France, Britain and elsewhere, anti-immigrant parties opposed to the influence of the European Union emerged in the lead. In France, the National Front won 26 percent of the vote to defeat both the governing Socialists and the Union for a Popular Movement, the center-right party of former President Nicolas Sarkozy.

In Britain, the triumph of the U.K. Independence Party, or UKIP, which won 28 percent of the vote, represented the first time since 1910 that a nationwide vote had not been won by either the Conservatives or Labour.

“The people’s army of UKIP have spoken tonight and delivered just about the most extraordinary result that has been seen in British politics for 100 years,” said Nigel Farage, UKIP’s leader. ...

Official results released overnight showed that populist parties strongly opposed to the European Union also trounced establishment forces in Denmark and Greece and did well in Austria and Sweden. The results, a stark challenge to champions of greater European integration, left mainstream political leaders stunned. ...

With the political landscape redrawn across Europe, some politicians, notably Nick Clegg, the British deputy prime minister and leader of the Liberal Democrats, the junior coalition partner, faced calls from their own party members to quit. The Liberal Democrats finished fifth in Britain and lost nearly all their seats at the European Parliament. ...

In Paris, the victory by the National Front, led by Marine Le Pen, prompted Manuel Valls, the French prime minister, to acknowledge: “It’s an earthquake.”

“We are in a crisis of confidence,” Mr. Valls added. “Our country has for a long time been in an identity crisis, a crisis about France’s place in Europe, Europe’s place in our country.”

President François Hollande of France called an emergency meeting of senior ministers after his Socialist Party finished a remote third. ...

European Parliament ballots often do not reflect voting patterns in national elections, which favor traditional parties. But in Britain, Mr. Farage, the U.K. Independence Party leader, depicted his triumph on Sunday as the harbinger of greater prominence in next year’s national elections, saying that his followers could hold the balance of power if neither the Conservatives nor Labour win an outright majority.

“We will go on next year to a general election with a targeting strategy and I promise you this: You haven’t heard the last of us,” he said.