It’s pretty smart for Trump not to participate. He gets to scope out the competition from the sidelines. Kinda like deferring after winning the coin toss. The Fox News debate is the one that count anyway.
There is also a showmanship aspect to this as well.
Why show his cards at some rinky dink debate. Wait for the big one.
He doesn’t need to star in some Off Broadway show to work out the kinks. Go straight to Broadway. In this case, Fox.
No one will know what is coming. Not the fellow debaters. Not the press. Not Fox.
I think this also allows Cruz to not be overshadowed by Trump.