The poll, conducted Monday through Wednesday, is in contrast to a CBS survey conducted last week, when the Democratic ticket led the Republican ticket 48 percent to 40 percent, CBS said. In the latest poll, 12 percent indicated they were undecided and 1 percent said they wouldn't vote.

McCain officially was nominated as the GOP presidential candidate Wednesday after his vice presidential candidate, Alaska Gov. Sarah Palin, addressed the Republican National Convention in St. Paul, Minn.

McCain also closed the enthusiasm gap some with Obama, poll results indicated. Fifty-five percent of Obama's supporters told pollsters they were are enthusiastic about their choice, as did 35 percent of McCain's backers. Last week, just 25 percent of McCain's supporters expressed enthusiasm about their candidate, compared to 67 of Obama's backers.

The CBS News poll was conducted by telephone with 835 adults nationwide, including 734 registered voters. The overall sampling margin for error is plus or minus 3 percentage points.