Trump is brilliant. Most leftists are all in for Sanders. They look at Hillary as a lying member of the establishment. They (the party) will never let Sanders be the nominee. It will be HIllary barring some Warren scenario. And no leftist is going to make a huge effort to go out and vote for Hillary.
Trump does not need to debate Hillary. He is going to mock her to death. Its the smart move. Death by a thousand cuts.
If Sanders wins big in NH (possible), Warren may get in like RFK in 3/68.
We McCarthyites (Gene) never forgave.