Donald Trump said all the right things in his speech to Aipac this week — which is precisely why it was so terrifying. Speaking for the first time with a teleprompter, he delivered a calm, rational and unexceptionable address. He was right about the Iran deal, right about the threat to Israel and right about terror. The fact that his words directly contradict his views expressed barely a few days ago is, in this context, irrelevant, because it shows that he knows that different audiences require different approaches — and, as such, could be said to be mastering the art of politics, and thus electability. But in every other sense, of course, it is directly relevant that he should be so shameless in changing his tune to please his audience. Trump is entirely without principle and does not hesitate to pander to racism when it suits. He is not fit for any public office, let alone the presidency. Until Aipac, his inability to stand before a crowd without resorting to bullying and braggadocio has led to the comforting thought that he would be incapable of surviving the exposure of a presidential election. His Aipac speech showed that is almost certainly a false comfort.