Most politicians are willing to go pretty far out on rhetorical limbs to advance what they see as their political interest. What they don’t like is to be exposed as fools soon after doing so. The real importance of the “smoking gun” tape that ended Richard Nixon’s presidency was that it discredited his supporters for repeating what turned out to be lies, and convinced them that Nixon would go on doing that to them as long as they were willing to stick with him. They might have been willing to let him shred the Constitution, but they weren't willing to look like idiots.
Trump is repeatedly giving Republicans that same choice. So far, they've been willing to go along. But each time he pushes them, it makes it a little more likely they’ll eventually make the same choice that Republicans made in August 1974.