WASHINGTON  The Senate gave Ben S. Bernanke a second four-year term as the head of the Federal Reserve on Thursday after critics excoriated the central bank’s conduct in the years leading up to the financial crisis.

The 70-to-30 vote was the weakest endorsement ever extended to a chairman in the Fed’s 96-year history.

The confirmation was a victory for President Obama, who had called Mr. Bernanke an architect of the recovery, but also signaled the extent to which the Fed, once little known to the public, has become the object of outrage over high unemployment and bank bailouts.

In several hours of debate, senators said that the Fed had abetted, then ignored, the housing and credit bubbles and allowed banks to keep dangerously low capital reserves and to make reckless lending decisions that ruined consumers. Some even blamed Mr. Bernanke for the falling dollar and questioned his commitment to free enterprise.