France was not the only euro economy to stumble. Italy, where Prime Minister Matteo Renzi has also backed off austerity pledges to spur growth, slid back into a recession in the second quarter. Even in Germany, which had been leading what only a few months ago seemed to be the eurozone’s incipient recovery, the economy contracted 0.2 percent in the second quarter after a solid year of expansion.

Economists have been debating whether the robust growth in the years before 2008 will ever return — or whether a new dynamic, known as “secular stagnation,” has taken hold, hindering robust recoveries in growth and unemployment.

“It is too soon to tell whether secular stagnation is going to materialize,” Nicholas Crafts, a professor of economics and economic history at the University of Warwick, wrote in a recent paper published by Centre for Economic Policy Research in London. “But it does seem clear that Europeans should be much more afraid than Americans. The depressing effects of slower growth of productive potential will probably be felt more keenly in Europe.”

Like many eurozone countries, France was compelled to embrace some austerity to reduce its debt and deficit levels after the financial crisis, when global credit markets were imposing steep borrowing costs on countries that seemed to be living beyond their means.

Last year, Mr. Hollande announced a series of tax increases and 50 billion euros, or $66 billion, in spending cuts through 2017, which crimped the economy. And in aiming toward the 3 percent budget deficit target required for eurozone member countries, he also pledged to cut France’s deficit to 3.8 percent this year, from 4.3 percent in 2013.

France’s borrowing costs have plunged to record lows since the crisis. But French businesses and industrial activity have struggled to recover to precrisis levels, making it harder for the government to find the tax revenue needed to reduce the deficit. Hoping to offset the slowdown, Mr. Hollande announced in January new tax breaks for business to encourage hiring.

But last week, the French economy minister, Michel Sapin, warned that the economy had become so feeble that the government would no longer try to meet the deficit target. He said France would grow only 0.5 percent this year, half the rate originally expected, and would struggle to expand at a 1 percent growth rate next year. Other embattled economies, including Greece and Spain, have suffered as they slashed spending and raised taxes in a downturn to meet the European Union’s fiscal targets.