MIAMI, FL-- Florida Congressman Connie Mack IV is reversing himself, and will run for U.S. Senate, FOX News has confirmed.

"Yes. He is running for U.S. Senate, and he is making phone calls and assembling a team," Mack's senior adviser David James tells FOX. " He will have more to announce in the coming weeks ahead."

Last March, Mack surprised many when he officially decided not to enter the GOP fray after citing his desire to spend more time with his wife California Congresswoman Mary Bono Mack, and their young children.

The GOP field currently consists of former Florida Majority Leader Adam Hasner, retired Army Colonel Mike McCalister and former U.S. Senator George LeMieux. Florida Senate President Mike Haridopolos, exited the race after being an early front-runner.

The winner of the GOP primary will face U.S. Senator Bill Nelson, the incumbent, and highest-ranking Democrat out of Florida, who is up for re-election in 2012.

Mack has endorsed former Massachusetts governor Mitt Romney for president, and is serving as one of his co-chairmen in Florida. (read more)