Good move. If you pledge to do something stupid and later realize that stupidity, you shouldn't just do the stupid action to keep your word. The GOP won't be fixed unless more people start pushing back.
Are you saying that Kasich didn't realize what Donald Trump was all about? No, he knew
exactly what Trump is about, but he along with everyone else (myself included) could never have predicted that Trump would end up as last man standing. So I guess future such pledges should read something like "I pledge to support the party nominee, unless I don't like the nominee or the nominee does/says stupid things, in which case I'll stay home and not be bothered".
So again, I'm confused: why put a pledge like this in place at all, and make such a big deal about getting everybody to sign it? I seem to recall Trump saying that the pledge was pointless, and he was given all kinds of grief about saying that. He signs it, and so do all the other Republican candidates, but it sure appears as though Trump was right in thinking that the document was pointless. Typical politics, I suppose...