At some point I keep expecting Joaquin Phoenix to admit he’s behind the weird performance art that is Donald Trump’s presidential campaign. But tonight in Michigan during the Republican Debate, at a perfect moment to do so, Phoenix was nowhere to be seen. Since the beginning of this whole thing Trump has taken cheap, personal shots at the disabled, at war heroes, and at women. He’s also unleashed them on his opponents, who until recently had decided to take the high ground. And how did that work for them? Not very well. So in the past couple of weeks Marco Rubio has released a barrage of personal attacks, but he’s bringing a knife to a gun fight.