Democratic Sen. John Kerry (search) gained some ground on President Bush (searchamong swing voters in the last month, with several citing the presidential debates as a factor in their shift, according to a poll released Wednesday.

The Pew Research Center for the People & the Press (search) called back 519 voters who were either undecided in September or said they could still change their minds. That group tilted toward Bush in September and is now evenly split on Bush and Kerry.

By more than 3-to-1, the swing voters said Kerry did the better job in the debates.

Swing voters "have been drifting toward Kerry a little more than Bush," said Andrew Kohut, director of the Pew Research Center. "But everything about the remaining slice of the electorate says it's pretty much even."

The number of swing voters in that group either committed or leaning toward Kerry was 40 percent, up from 28 percent in September. The number either committed or leaning toward Bush was 38 percent, compared to 34 percent in September.

About half the group is firmly committed to a candidate and the other half are weighing their final choice. Swing voters make up about 15 percent of the overall electorate, according to Pew polling.

The 519 swing voters were called Sept. 8-26 and called back Oct. 21-25. The margin of sampling error is plus or minus 5 percentage points, slightly larger for subgroups.