President Donald Trump’s refusal to work cooperatively with the Senate has caused many to complain that it has become a “circular firing squad.” Now he has refused to endorse his Senate Majority Leader, John Thune of South Dakota, for reelection — and Thune sarcastically slapped him back."Alright,” Thune said when confronted about Trump’s betrayal, according to Punchbowl. “Well, that’s nice of him. I GUESS. I don’t know what do you say on that. …