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Although the Battleground poll found that more voters think Mr. McCain is running a negative campaign, she said, some of the attack themes against Mr. Obama were working.

She argued, however, that the poll data continue to suggest that Mr. Obama’s supporters are more energized than are Mr. McCain’s, that the Obama campaign has the potential to alter the traditional political map, and that independents and Democrats are united in their belief that the country is “on the wrong track.”

“I think the indicators are very volatile right now and both sides are going to fight very hard” for the independent vote, she said.

Mr. Nienaber noted that the party conventions, the running mates and the presidential debates can alter the dynamics of the race.

He said Mr. McCain’s unexpected strength on such core issues as energy prices and the economy is a good sign for Republicans, complementing Mr. McCain’s pronounced lead over Mr. Obama on national security issues.

In the Battleground poll, Mr. McCain and Mr. Obama each received 43 percent on the question of which candidate could “keep America prosperous.” Mr. Obama led 47 percent to 41 percent when the question was asked in May.

“No Democratic candidate has ever won who didn’t enjoy a big lead on that question,” Mr. Nienaber said.

  • S.A. Miller contributed to this report.