Older voters are angry the Senate was unable to pass a Medicare drug benefit, and a quarter of them are vowing to vote against an incumbent candidate if lawmakers remain gridlocked, an AARP poll says.

"Our poll suggests there is a very strong potential for an anti-incumbency mood," said Chris Hansen, director of advocacy for AARP, the nation's largest lobbying group for senior citizens. "People aren't going to accept Republicans blaming Democrats or Democrats blaming Republicans. Incumbents are going to pay a price."

The Senate left for summer recess last week after Republicans and Democrats were unable to reach agreement on four different Medicare drug proposals. The House has passed a $320 billion proposal to provide seniors on Medicare with a drug benefit.

The poll, conducted July 31-Aug. 4, used a national sample of 1,070 voters age 45 and older. It was conducted for AARP by ICR of Media, Penn., and has a margin of error of plus or minus 2.5 percentage points.

Six in 10 of the respondents, or 61 percent, said they were angry the two parties could not reach a compromise. Of that group, 32 percent described themselves as very angry. The other 29 percent described themselves as somewhat angry. Twelve percent of respondents were not too angry and 20 percent were not at all angry. Eight percent either didn't know or refused to answer.

Twenty-six percent of those polled said they would vote against their senator if he or she allows partisan differences to prevent passage of the legislation.