The United States economy has lost the momentum it appeared to be building earlier this year, as the latest government statistics showed that it expanded by a mere 1.5 percent annual rate in the second quarter.

The mired recovery makes the United States more vulnerable to trouble in Europe and, at home, the potential expiration of several tax breaks and other buoyant measures at the end of the year, known as the fiscal cliff. It also illustrates the election-season challenge to President Obama, who must sell his economic record to voters as the recovery slows.

Growth, as measured by the gross domestic product, lagged as consumers curbed new spending and businesses held back. Several bright spots in the first three months of the year, including auto production, computer sales and large purchases like appliances and televisions, dimmed or faded away altogether in the second quarter, and government at all levels continued to cut spending. Growth was not strong enough to drive down the unemployment rate, which has stalled above 8 percent in recent months.

The lackluster figure immediately gave Mr. Obama’s opponents the opportunity to question the federal government’s response to the financial crisis, though a vast majority of economists agree that the stimulus and the bank bailouts saved jobs. House Speaker John Boehner said the G.D.P. report, released Friday by the Commerce Department, showed “the need to stop all of the looming tax hikes.” The report also spurred calls from liberals for the government to do more.