Among those who watched the much-anticipated debate between Biden, Barack Obama's running mate, and Republican nominee John McCain's running mate, Sarah Palin, 51 percent said Biden did a better job than Palin, while 36 percent of viewers said Palin won the debate.

The majority of respondents said Biden, the senior senator from Delaware, and Palin the Alaska governor, did better at the Washington University forum than they expected.

The poll found that 64 percent of viewers said Biden did better than they expected, while 84 percent said Palin did better than they expected her to do.

The poll's margin of sampling error is plus or minus 4 percentage points, CNN said. The sample size was not immediately reported.