But conservative outside groups who sense a pickup opportunity in the Sunshine State are doing their best to make up the difference. American Crossroads has reserved more than $6 million in television airtime to oppose Nelson, and casino mogul Sheldon Adelson recently donated $1 million to Freedom PAC, a pro-Mack super PAC. Mack and his allies won't have to spend much to win the GOP nomination. After a series of more high-profile Republican candidates dropped out of the race, former Rep. Dave Weldon and retired Army Col. Mike McCalister are his main competition for the GOP nod, but Mack is expected to cruise to victory in the August 14 primary. The Mason-Dixon poll did not test the primary. The poll was conducted July 9-11 for the Miami Herald, Tampa Bay Times, El Nuevo Herald and two in-state cable news television stations. Mason-Dixon Polling & Research surveyed 800 likely voters, for a margin of error of plus-or-minus 3.5 percentage points.