Democratic presidential candidate Barack Obama on Tuesday brushed aside a survey that showed him losing support among white women voters to John McCain since the Republican standard-bearer named Sarah Palin as his running mate.

A Washington Post/ABC News survey published on Tuesday found most of McCain's surge in the polls since the Republican National Convention was due to a big shift in support among white women voters.

"The notion that people are swinging back and forth in the span of a few weeks or a few days this wildly generally isn't borne out," Obama told reporters during a campaign stop in Riverside, Ohio.

His campaign manager, David Plouffe, was more pointed when asked about the findings at a briefing on Monday, telling a Washington Post reporter, "Your poll is wrong."

"I don't think you'll find many others that back up a 20-point reversal," Plouffe said. "We certainly are not seeing any movement like that."

The poll found that the race for the White House is a virtual tie since the parties' nominating conventions, with Obama, an Illinois senator, at 47 percent support of registered voters and McCain, an Arizona senator, at 46 percent.

An NBC News/Wall Street Journal poll released on Tuesday also showed Obama leading McCain by 47 percent to 46 percent, a statistical dead heat. Obama's lead in that survey was down from 3-point advantage in August and a 6-point edge in July, NBC said.

Before the Democratic National Convention in late August, Obama held an 8-point lead among white women voters, 50 percent to 42 percent, according to the Washington Post/ABC News poll. After the Republican convention in early September, McCain was ahead by 12 points among white women, 53 percent to 41 percent, that survey found.

"There is no doubt that Governor Palin attracted a lot of attention this week," Obama told the news conference. "It has brought excitement to the Republican Party."

"What we're going to have to do is to see how things settle out over the next few weeks when people start examining who's actually going to deliver on the issues that people care about: Who's got an education policy to improve the prospects for our children? Who's got a health-care plan that's going to help a whole bunch of women out there?" he said.

McCain surprised the electorate ahead of the Republican convention by naming the little-known Alaska governor as his vice presidential running mate. Palin received high marks among supporters for her convention address, which included a scathing attack ridiculing Obama's experience and record.

Obama, who would be the first black U.S. president, defeated Hillary Clinton in the battle for the Democratic nomination, a long and bitter struggle that left many of the former first lady's supporters disaffected and angry.

Many of her backers were further angered when Obama ignored her in picking a vice presidential running mate, choosing instead longtime Delaware Sen. Joe Biden. A key question for the Obama campaign has been whether he would be able to maintain the support of Clinton's supporters.