While Rick Santorum is in Florida seeking to revive his presidential campaign, a man in Wyoming might hold the key to extending his candidacy, and the entire fight for the Republican nomination. Foster Friess is the largest financial backer of the political entity running an independent campaign to boost Mr. Santorum in the GOP race. Mr. Friess said this week he isn't likely to help Mr. Santorum ahead of Tuesday's Florida primary, because it's "not realistic" that the former Pennsylvania senator can prevail in the winner-take-all contest. But Mr. Friess, 71 years old, said he plans to fund television advertisements...