Steven A. Greenberg, a pollster from Siena College, which conducted the survey, said the special election, though it was taking place in a traditionally Democratic section of Brooklyn and Queens, had become a chance for voters to register their unhappiness with the national economic and political climate. The poll, which had a margin of sampling error of plus or minus three percentage points, found that 54 percent of likely voters in the district had an unfavorable view of Mr. Obama, and nearly three quarters said the country was headed in the wrong direction…

Mr. Turner has repeatedly sought to link Mr. Weprin with Mr. Obama; Mr. Weprin, for his part, has not highlighted the president in his campaign literature, and has instead featured the state’s popular Democratic governor, Andrew M. Cuomo.

As a sign of how worried Democrats are, they are already engaging in back-room finger-pointing about who is most responsible for Mr. Weprin’s plight. In Washington, several Democrats said in interviews that they believed the race was slipping away from their party; several cited Mr. Obama’s unpopularity as the cause, but others blamed Mr. Weprin for running a weak campaign.