Democrat hedge fund billionaire and global warming activist Tom Steyer spent $74 million on Tuesday's midterm elections, making him this election season's single-largest donor. Almost $67 million of Steyer's campaign war chest was spent on his super PAC, NextGen Climate Action, reports Forbes. However, as The Hill points out, Steyer's big money spending spree may garner him one of the hedge fund titan's most middling returns to date. In Colorado, Steyer's super PAC has spent $7 million against GOP Senate candidate Rep. Cory Gardner and $421,202 for Democrat Sen. Mark Udall. The RealClearPolitics average of polls has Gardner up 2.5%....