Attorney Mike Lee joined a field of candidates looking to knock off Sen. Bob Bennett on Tuesday, setting off a scramble for support from conservative delegates discontented with the three-term senator.

Bennett welcomed Lee into the Senate race and said his decision to run was not surprising, nor will it affect his campaign strategy.

"We are focused on running our campaign regardless of who the challenger is going to be," Bennett said. Lee "has good credentials, but he is getting off to a late start. We'll see how credible he is."

Lee's entry had been widely anticipated for weeks, and he had been holding a series of town hall-style meetings throughout Utah where he spoke to conservative activists about perceived threats to the Constitution.

Bennett is under fire from conservative Republicans over his support for the first round of bank bailouts during the Bush administration and his health care reform proposal, as well as a generally moderate voting record.

He is also seen as a consummate Washington insider who has become detached from Utah issues.

"There's huge dissatisfaction" with Bennett, said Jared Law, a Utah organizer for the 9/12 Project. "Nobody who understands the principles of liberty and the Constitution wants to see Senator Bennett re-elected."

Lee joins a field of candidates that includes businessman Tim Bridgewater, conservative activist Cherilyn Eagar and James Russell Williams who are competing to capture those discontented voters.

Law said that, while he supports Eagar, the vast majority of members of the Tea Party movement and the 9/12 Project would have no problem voting for either Lee or Eagar. Businessman and restaurateur Sam Granato is the lone Democrat running for the seat.

Attorney General Mark Shurtleff, who was seen as Bennett's strongest challenger before quitting the race to care for an ill daughter, said 1,000 Republican delegates had pledged to support him, and he urged them to support Lee.

A candidate can secure the nomination by getting the votes of 60 percent of the 3,500 GOP delegates. Otherwise, the top two candidates must square off in a primary.

Shurtleff said that government needs to change how it operates, but the other candidates don't have the capacity to beat Bennett.

Quin Monson, associate director of the Center for the Study of Elections and Democracy at Brigham Young University, said Lee is an intriguing candidate because he is smart and well-spoken, but it remains to be seen how he can perform as a candidate and whether he can raise money to compete.

Monson said he still figures Bennett is the favorite to survive the Republican convention, but the race now is "certainly more interesting than it was. I think Mike Lee is a very credible candidate."

Lee said he does not plan to run an anti-Bennett campaign, but rather to focus on returning government to its constitutional roots.

"Our national government can't do everything. In fact, it's not supposed to," he said.

That doesn't include things like providing health care or bailing out banks and automakers, said Lee. He supports amending the Constitution to balance the budget and impose 12-year limits on members of the House and Senate.

Lee has represented EnergySolutions in the radioactive waste company's effort to import foreign waste to the state and said Tuesday that Utah and the Northwest Interstate Compact On Low-Level Radioactive Waste Management improperly sought to stop the company from disposing of 1,600 tons of low-level radioactive waste from Italy at its Utah site.

"The Constitution stands firmly on their side in that case," he said. Lee said he could support legislation to limit -- but not prohibit -- the importation of foreign waste to a percentage of the landfill's total capacity.

"I don't want Utah to be the world's radioactive waste dumping ground any more than anybody else does," he said.

Bennett has opposed legislation sponsored by Democratic Rep. Jim Matheson and Republican Rep. Jason Chaffetz that would prohibit the waste and Bennett stalled the bill in the Senate after it passed the House.

Rival candidate Eagar said in a statement Tuesday that she opposes the disposal of the foreign waste in the state, but would like to see the state exercise the authority to bar it.

Lee was flanked by former U.S. Rep. Jim Hansen, former Gov. Norm Bangerter and eight state legislators who are supporting his candidacy.

Hansen, who served 11 terms in the U.S. House, said he saw members of Congress "put their own aggrandizement above the principles they have."

Bangerter said that "the basic challenge we have in this country is to stay rooted in basic principles."

"We've forgotten our fiscal responsibility. We've forgotten that if you're going to spend it, you've really got to pay for it, and we've forgotten that in both political parties," the former two-term governor said.

Donald W. Meyers contributed to this story.