The poll, conducted by Dresner, Wickers and Associates for Bruning’s exploratory committee, surveyed 404 likely GOP primary voters and shows Bruning with a 61 percent favorability rating, compared to 52 percent for Hagel.

Bruning formed his exploratory committee last month, saying he would run only if Hagel retires. Last week, he shifted gears and said he might mount a primary challenge, citing Hagel’s vote for a strict withdrawal deadline in Iraq and the two-term senator’s suggestions that President Bush could be impeached.

He added: “Certainly, I don’t make any decisions based on polls, but they do give you an idea of what Nebraskans are thinking. It clarifies for me what I’ve been feeling as I’ve traveled around.”

In response, Hagel’s camp ratcheted up the rhetoric, clearly taking exception to Bruning’s recent overtures about the 2008 race. In a statement, Hagel political director Kevin Chapman called Bruning “a chameleon” and cited his formerly liberal views.

A Nebraska political blog recently published excerpts from newspaper columns that Bruning wrote as a law student in 1992. In one article, Bruning expresses support for abortion rights, gay rights, gun control and affirmative action.

“With his record of credibility, we don’t put much stock in ‘polls’ Jon Bruning pays his pollster to produce,” Chapman said. He pointed to Hagel’s work with President Bush on issues besides Iraq and said it was “laughable” that Bruning claims to be more Republican than Hagel.

Hagel’s unfavorability rating among Republicans is at 36 percent, while Bruning has an eight percent unfavorability rating and a 91 percent name-identification score, according to the poll.

Just less than half of voters said it is time to give someone new a chance in Hagel’s seat, while 38 percent said Hagel deserves another term.

The poll also showed Bruning leading former Rep. Hal Daub (R-Neb.) 55-16 in a head-to-head match-up. Daub has indicated he might run if Hagel retires.

The poll contained no head-to-head numbers for Bruning against former governor and current U.S. Agriculture Secretary Mike Johanns (R), who has expressed no interest in the race, or against Omaha Mayor Mike Fahey (D), who has said he would run only if Hagel retires.

Hagel has yet to indicate whether he will run for reelection to the Senate in 2008. He has hinted that he might run for president, and he has also suggested that he might run for neither.

Hagel called a press conference last month in which he said he would make a decision about his political future at a later date.