UPDATED CBS News and Knowledge Networks have conducted a nationally representative poll of 473 uncommitted voters to get their immediate reaction to tonight's vice presidential debate.
After the first presidential debate, a similar survey showed that more uncommitted voters identified Barack Obama as the winner
Final numbers from tonight's poll have yet to come in, but we do have some early results. (These numbers may change as more respondents complete the survey.) They suggest that once again more voters have responded favorably to the Democratic candidate.
Forty-six percent of the uncommitted voters surveyed say Democrat Joe Biden won the debate, compared to 21 percent for Republican Sarah Palin. Thirty-three percent said it was a tie.
Eighteen percent of previously uncommitted percent say they are now committed to the Obama-Biden ticket. Ten percent say they are now committed to McCain-Palin. Seventy-one percent are still uncommitted.
Both candidates improved their overall image tonight. Fifty-three percent of those surveyed say they now have a better impression of Biden. Five percent say they have a worse opinion of the Delaware senator, while 42 percent say they debate did not change their opinion.
Fifty-five percent say they now have a better opinion of Palin. Fourteen percent say they have a worse opinion, while 30 percent say their opinion hasn't changed.
After the debate, 66 percent see Palin as knowledgeable about important issues – up from 43 percent before the debate. But Biden still has the advantage on this – 98 percent saw him as knowledgeable after the debate. That figure was 79 percent before the debate.
Uncommitted voters' views of Palin's preparedness for the job of vice president also improved as a result of her debate performance - but they are still nowhere near the percentage that thinks Biden is prepared.
Fifty-five percent say Palin is prepared for the job, up from 39 percent before the debate. Ninty-seven percent say Biden is prepared, up from 81 percent pre-debate.
Although Palin made some gains on the question of whether she could serve as president if needed, she rose just 9 points on that measure. Now 44 percent say the Alaska governor could be an effective president. Ninety-one percent said Biden could be effective as president, up from 66 percent before the debate.
We will have a full report on the poll later on. Uncommitted voters are those who don't yet know who they will vote for, or who have chosen a candidate but may still change their minds.