With the vice presidential debate just one day away, Alaska Gov. Sarah Palin is increasingly a drag on the Republican ticket, with 51 percent now saying she is not qualified to be president compared with 37 percent who say she is, according to a new poll by the Pew Research Center.

The result of the survey, conducted Sept. 27-28, is a reversal from numbers recorded just after the Republican National Convention, where Palin delivered what was widely considered a strong performance. At that time, 52 percent said she was ready to step in as president. Palin is viewed, however, as more “down to earth” than the Democratic vice presidential candidate, Sen. Joseph Biden (Del.), while Biden is seen by a large majority as better-informed.

At the top of the ticket, Democratic presidential candidate Sen. Barack Obama of Illinois has gained what Pew calls a “significant lead” over his Republican opponent, Sen. John McCain of Arizona — 7 points among registered voters.

The survey, conducted just after the Sept. 26 presidential debate, found that Obama has moved to a 49-42 percent advantage, a marked improvement on previous results that had showed the race virtually even in mid-September and early August.

Obama bested McCain in the debate, according to the poll, with 72 percent rating his performance as excellent or good compared with 59 percent giving the same measure to McCain. There is no difference in the minds of those polled on which candidate would use better judgment in a crisis, a reflection not only of Obama’s steady debate performance but perhaps also a reaction to McCain’s decision not to debate and then his subsequent change of mind.

Obama also is viewed as far better-equipped to deal with the financial crisis. And he has widened his lead as the candidate best able to handle the overall economy, jumping from a 9-point lead in a previous pool to an 18-point spread, 51 to 33 percent.

Obama in the past few weeks has made significant gains among those in his party, including white Democrats. Many backed Obama’s chief primary opponent, Sen. Hillary Rodham Clinton of New York, and there have been fears among Democrats that they will fail to get behind Obama as a result of the bitter contest. Obama also is gaining in battleground states and among baby boomers and affluent voters.

McCain continues to lead Obama among white voters overall, with his support concentrated among men, older voters, those with less education and those living in the South.

The poll surveyed 1,505 adults, including 1,258 registered voters. The margin of error was 3.5 points among registered voters and 3 points among all voters.