Grassley is well ahead of three Democratic opponents in a Public Policy Polling survey released Friday. The poll also shows Grassley enjoys a unified base of GOP support in a year in which incumbents in both parties have faced challenges.

In a match-up with Democrat Roxanne Conlin, Grassley leads 57-31 percent.

Against Democrats Tom Fiegen and Bob Krause, Conlin's primary rivals, Grassley led 56-28 and 56-26, respectively.

Conlin is the front-runner for the Democratic Senate nod. The primary vote is next Tuesday.

Grassley fits the mold of an endangered incumbent senator. Like Sen. Bob Bennett (R-Utah), who lost the GOP nomination at the Republican state convention earlier this year, Grassley voted for the Wall Street bailout in 2008.

But the May 25-27 survey has him getting 88 percent of the Republican vote and 25 percent from Democrats.

If Conlin is the nominee, she'll have to work hard to raise her name identification. Nineteen percent of those surveyed have a favorable opinion of Conlin, while 29 percent had an unfavorable rating and 53 percent of the 1,277 Iowa voters surveyed had no opinion of her.