If he didn't, the lamestream media and the Clinton campaign (yes, I repeated myself) would cast it as "Trump is afraid to debate Hillary".
The only way to beat this is for the Republicans to present a united front, and run their primary debates properly. Several people have made good proposals, like:
At the end of the primary season, the Republicans say: we are holding a debate in this manner. You can join us, if you want. Our candidate won't be attending a debate run by the media.
I’m not saying ignore the debates - but rather, force forums that are equal or play to his strengths.
For example - Town Hall events, with no political operatives in the audience. moderators only call time or enforce speaking rules.
Agree. This MUST be done by next election, and there MUST be true conservatives like Allen West, Ann Coulter, Breitbart, etx as moderators developing questions.