SARASOTA, Fla. (CBSMiami/AP) – Republican Congressman Connie Mack IV will enter the U.S. Senate race seeking to challenge Democratic Senator Bill Nelson, Mack announced on a FOX News’ Sean Hannity Show Monday night.

He enters the Republican primary as the front-runner after a Quinnipiac University poll earlier this month showed he pulled support away from a GOP field that wasn’t stirring much excitement. The poll had Mack about 23 points ahead of his closest opponent. He let it be known through a spokesman a month ago that he was preparing to enter the race but hadn’t publicly discussed it.

Between now and the Aug. 14 primary Mack will have to prove he deserves the nomination and that his support isn’t just based on his famous name. His father, Connie Mack III, previously held the same Senate seat and his great grandfather is the legendary Hall of Fame baseball manager.

Mack’s opponents are already attacking him, hoping to take advantage of the poor public approval for Congress. Also in the race are former state Rep. Adam Hasner, retired Army Col. Mike McCalister, former Ruth’s Chris Steak House CEO Craig Miller and former U.S. Sen. George LeMieux, who was appointed by then-Gov. Charlie Crist to fill the last 16 months of Mel Martinez’ unexpired term.

The rest of the field is already portraying Mack as a Washington insider and part of the problem with Congress. Mack sits on the Oversight and Government Reform and the Foreign Affairs Committee.

Mack was first elected to Congress in 2004 after serving three years in the state House. He’s giving up easy re-election to face what could be a bruising primary for the right to face well-financed two-term incumbent Bill Nelson. Mack hasn’t had a difficult general election challenge, having won his four elections by an average of 35 percentage points.

Mack earlier this year said he would seek re-election and endorsed Senate President Mike Haridopolos for Senate, but Haridopolos has since dropped out of the race and is now endorsing Mack.

Mack’s opposition to the Arizona immigration law that many conservatives back and his support of embryonic stem cell research will likely be issues during the primary. Critics have also said Mack, who is married to California Congresswoman Mary Bono Mack, doesn’t spend enough time in his district.

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