.... Well .... Duh. Of course the base will walk .... That's why the Democrats and GOPe are trying to guarantee that the Wall won't be built .... It's called "Divide and Conquer." It's a tactic that the Democrats use very well .... And sadly it a tactic that the GOP falls for almost every time thanks to the co-operation of the useful idiot GOPe.
They (Rats, GOPe) the uniparty have gotten Trump to rollover on many of his big campaign promises. Dreamers, refugees, PP, deporting all illegals, Paris Accords, expanding NATO, etc. If they can keep him from building the wall they know his base will stay home in 2018 (and 2020 if he is renominated).