Almost all politicians find President Trump poisonous. They're struggling to keep their jobs and their sanity. The best thing they can do is not call attention to themselves by disagreeing with a man in power who will railroad them into the ground.
The ones dissenting are the ones with nothing else to lose. All that means to us is that no progress will actually be made, only the status quo will be maintained. If they have an agenda, it's unpopulous and therefore not winnable. Elected officials will not take that chance. We see that in droves of Republicans not seeking re-election. Democrats have to walk a fine line to stay on the Tea Party's good graces or they will face insurmountable odds of even getting a nomination, let alone a support base.
Neither party actually has a platform worth voting for on issues. It's either support Trump or Not. Right now, the Prez has a fair amount of base, it's whether he can increase voter confidence to get a re-nomination. Challengers such as Kasich need to keep pressure to allow the remaining Republicans to return to how the party should be functioning.