Remember there’s a difference between the rank and file Congressmen and Senators, and the party bureaucrats and donors. The party higher ups and the donors will never willingly accept a candidate they don’t control. The rank a file politicians who’s membership in the elite is based on their election to office are more vulnerable. They might not want Trump, but if they understand that denying Trump the nomination is likely to cost them reelection, as a result of a huge protest vote against all Republicans, some of them might begin supporting him.
You make a good point, mbrfl. We can hope and pray for that possibility.