They won't take the pledge because they are cowards.
And, they do face daunting and formidable enemy...the media in this country which has been taken over by hard leftist.
Paul Ryan is the last to take the chance...few years ago. He put forth proposal looking to fiscal responsibility...and within 3 days the Democrats had a look-alike Ryan wheel-chairing an old woman off a cliff...and the Left-Wing Media not only did not condemn this perverse absurdity...they applauded it.
So, the folks...the Traditional Americans... whose forefathers built this place into the greatest society ever known...are looking for a Republican with some intestinal fortitude.
They think they have found their man, but he seems to be bat-shit-crazy, and they are deciding whether they are desperate enough to take a risk on Crazy to defeat the combined malefactions of Incompetence & Corruption & Socialism.