One of those Hillary surrogates is President Obama. Given that he has a real talent for mockery — this, not uplift or persuasion, is what he’s best at — he’s going to have a field day going after Trump. But there is no evidence that he’s ever been able to transfer enthusiasm for himself to any other politician. And his high approval ratings, 58 percent in the last Washington Post/ABC poll, might not survive him being out there as a partisan hatchet man every day.