WASHINGTON (Reuters) – Republican presidential candidate John McCain has gained huge support among white women since naming Sarah Palin as his running mate and now leads Democrat Barack Obama among those voters, according to a survey published on Tuesday.

The Washington Post/ABC News poll found that much of McCain's surge in the polls since the Republican National Convention is attributable to the shift in support among white women.

The race for the White House is now a virtual tie, with Obama at 47 percent support of registered voters and McCain at 46 percent, the poll found.

Before the Democratic National Convention in late August, Obama held an 8 percentage point lead among white women voters, 50 percent to 42 percent, but after the Republican convention in early September, McCain was ahead by 12 points among white women, 53 percent to 41 percent, the poll found.

Asked about the findings during a briefing on Monday before the poll was published, Obama campaign manager David Plouffe told a Washington Post reporter, "Well, your poll is wrong."

"I don't think you'll find many others that back up a 20-point reversal," Plouffe said during the briefing at Obama's campaign headquarters in Chicago. "We certainly are not seeing any movement like that. Polls, time to time, particularly on the demographic stuff, can have some pretty wild swings."

McCain surprised the electorate ahead of the Republican convention by naming Palin, the little-known Alaska governor, as his vice presidential running mate. She 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 rival 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 president, choosing instead long-time 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.