If Hillary Clinton was the President, then one of her supporters would be pointing out the exact same thing.
My point being, it is overwhelmingly likely that the performance of the Dow Jones would not have been markedly different under a different administration. The President has far less influence on the general performance of the economy, of which the Dow is an indicator, than people like to believe. And that is true even during a recession or crisis of some sort, where the President has more room to exert their influence and has more direct responsibility. In the relatively economically stable times of the past 6 months, I feel entirely comfortable in believing that Donald Trump has little, if not nothing, to do with this.