WASHINGTON — A pair of one-night polls gave Barack Obama a clear edge over John McCain in their first presidential debate.

Fifty-one percent said Obama, the Democrat, did a better job in Friday night's faceoff while 38 percent preferred the Republican McCain, according to a CNN-Opinion Research Corp. survey of adults.

Obama was widely considered more intelligent, likable and in touch with peoples' problems, and by modest margins was seen as the stronger leader and more sincere. Most said it was McCain who spent more time attacking his opponent.

About six in 10 said each did a better job than expected. Seven in 10 said each seemed capable of being president.

In a CBS News poll of people not committed to a candidate, 39 percent said Obama won the debate, 24 percent said McCain and 37 percent called it a tie. Twice as many said Obama understands their needs than said so about McCain.

Seventy-eight percent said McCain is prepared to be president, about the same proportion of uncommitted voters as said so before the debate. Sixty percent said Obama is ready — a lower score than McCain, but a solid 16-percentage-point improvement from before the debate.

In another Obama advantage in the CBS poll, far more said their image of him had improved as a result of the debate than said it had worsened. More also said their view of McCain had gotten better rather than worse, but by a modest margin.

The CNN poll involved telephone interviews with 524 adults who watched the debate and had a margin of error of plus or minus 4.5 percentage points. The CBS survey involved online interviews with 483 uncommitted voters who saw the debate and had an error margin of plus or minus 4 points. It was conducted by Knowledge Networks, which initially selected the respondents by telephone.

Both polls were conducted Friday night.

Polls conducted on one night can be less reliable than surveys conducted over several nights because they only include the views of people available that particular evening.