Bush, Rubio, and Kasich are not loons. They are basically the same as Hillary on all except the "wedge" issues. They are plain-Jane centrist establishment candidates, just like Hillary. On the Democratic side, Sanders polls better against any of the Republican candidates than Hillary. She's not popular. But she's the only establishment candidate that the Democrats have. She'll get the straight-column voters on election day, but will have a hard time convincing a majority of more thoughtful people - or firing people up enough loyal people to actually come out and pull the lever. Sanders fires people up, no question about it. As the populist candidate, I wouldn't count him out just yet. Trump will have trouble getting past the nominating convention even if he wins a plurality of delegates. Between superdelegates and pooling of other candidates' delegates, I doubt he could secure the nomination.
But who am I? LOL.