He is a lunatic. If you look at photos of him while campaigning that is the first word you will think of, at least that is what I thought when I saw pastey faced Kasich.
He didn't really want to run. The establishment encouraged a bunch of people to run in states that were must wins for the nomination, so they could carry their home state, and nobody would get the minimum total of delegates. That way they could give their delegates to Jeb, and he would be the nominee as a safe compromise. I don't know what Kasich was promised, but obviously he didn't get it.
Lots of words come to mind, but lunatic will do.