The European Parliament is a largely powerless talk shop. So the status quo in Europe is not deeply threatened by the recent election of radicals in England, Denmark, France, Spain and Greece. They are opposed to more European centralization and in favor of rolling back the powers of the European Union.

The protest votes do mark a limit, however, to how fast the European Union can move toward centralized decisions that overcome the structural weaknesses of the euro currency. They also expose the deep division between the cautious German approach to Europe's economic and financial difficulties and the advocates of aggressive monetary and economic policies to attack Europe's economic stagnation. And they suggest that a major political crisis facing France could weaken the EU in the long run.

Given Germany's dominant position in the European economy and the general consensus in Germany that Angela Merkel's government is on the right path, the elections to the European Parliament are not likely to have any profound impact on the critical decisions regarding the euro that will be taken in the near term.

Where they are most likely to have an impact is primarily on the government of France and to a lesser extent on the decision of Britons whether to stay in the European Union.

Britain already has an arms-length relationship with the EU. It is not a part of its monetary union, for example, and resentment of rules laid down by the EU is widespread. The strong showing of the anti-EU United Kingdom Independence Party (UKIP) in the elections to the European Parliament is likely to strengthen the hand of Britain's Conservative prime minister, David Cameron, as he negotiates with the EU on the terms of Britain's continued membership. Cameron's success in gaining favorable new terms will be decisive in the British referendum he has promised to hold on continued membership.

But in France the surprise success of the right-wing, xenophobic and even anti-Semitic National Front in the European parliamentary elections is real cause for concern. The party, led by its founder's daughter Marine Le Pen, an outspoken admirer of Russia's Vladimir Putin, outpolled the ruling Socialist Party and its conservative Gaullist opponents, although it gained only 25 percent of the vote in low turnout.

Marine Le Pen was well positioned to collect classic protest votes against Muslims, African immigration, a stagnant economy with high unemployment, and the revolving door of technocratic and anti-populist governments. Her success underscored the plummeting popularity of President Francois Hollande, who in two years has been unable to revive the French economy.

Mr. Hollande probably wishes he had more flexibility to use borrowed funds to stimulate the economy. That is barred by EU rules on deficit spending. Alienated National Front voters were showing their disdain for a government that plays by the EU rules.

The European system depends on a continued close alliance between France and Germany. If French voters are fundamentally dissatisfied with what has been a beneficial relationship, the whole European system faces real trouble ahead.