Right now, he's the one guy standing between Rudy and the White House, and Fred's my candidate if he enters.
If Thompson enters the race, he'll immediately pick up a lot of undecideds and much of Rudy's support will jump ship. Of course many McCain supporters are only there because he's known and he's not Rudy. He'd tank within days.
I truly doubt that. And the ones that jump to Thompson did not really want to support Rudy in the first place. I hate to say this, but If Thompson runs the party will split and Hillary will win.
Fred would draw from three of the main contenders immediately: Rudy, McLame, and Newt, all for different reasons. He'd draw from Newt's people because he's a conservative who can win, and from Rudy and McLame's because he's more conservative than Rudy.