Presidential candidate Donald Trump is now taking on one-time Obama "car czar" Steve Rattner.On Monday, Trump fired off a tweet telling Rattner: "I think you should have gone to prison for what you did, I guess Obama saved you." He ended the tweet telling Rattner to watch: "I will win!" It was unclear what activity Trump was referring to that should have landed Rattner in jail. Trump did not respond to CNNMoney's request for comment. In 2010, Rattner did pay $10 million in fines when he settled with the New York state attorney general for his alleged involvement in a...