While he declined back in March to run for the U.S. Senate seat his father held for two terms, U.S. Rep. Connie Mack is preparing to enter the crowded Republican primary field of candidates looking to knock off Democratic incumbent U.S. Sen. Bill Nelson in 2012.

Media outlets at the state and national level reported on Wednesday night that Mack had reconsidered his decision and would enter the race. At the end of June, Mack endorsed state Senate President Mike Haridopolos, R-Merritt Island, for the Republican nomination to challenge Nelson. Haridopolos ended his bid for the U.S. Senate a few weeks later in mid-July.

Sources close to Mack informed Sunshine State News on Thursday that the Republican congressman would be entering the race in coming weeks.

While conservatives have taken aim at Mack’s opposition to the Arizona immigration law, Heritage Action, a group affiliated with the iconic conservative organization the Heritage Foundation, released its congressional rankings in August and ranked Mack as the most conservative Floridian in the U.S. House. From his perch as the chairman of the U.S. House Subcommittee on the Western Hemisphere, Mack has been a leading critic of the Castro brothers in communist Cuba and Venezuelan strongman Hugo Chavez.

In recent months, Mack has been pushing a plan  to reduce the size and scope of the federal government and balance the budget by 2019. The proposal, which Mack and co-sponsor U.S. Sen. Mike Enzi, R-Wyo., have dubbed the “Penny Plan," would mandate a 1 percent reduction in federal spending from 2012 until 2017, before imposing a spending cap in 2018. That cap would mandate the total cost of the federal government not to exceed 18 percent of the total gross domestic product.

Mack and Enzi maintain that their proposal would cut $7.5 trillion from the federal government over the next decade. The measure has earned the backing of a number of prominent Republicans in Congress as well as conservative organizations like the National Taxpayers Union and FreedomWorks, a Washington-based tea party movement organization led by former U.S. House Majority Leader Dick Armey.

Before announcing he was not running, Mack was doing better against Nelson in the polls than the other Republican candidates. A poll from Ron Sachs Communications and Mason-Dixon released in February found Nelson beating Mack by 5 percent, giving the Democratic incumbent a closer match-up than Republicans who had already announced they were running.

Some of the other candidates in the Senate race reacted to Mack’s looming entry on Thursday.