I firmly believe that the "responsible" Republicans -- those who didn't already start on the Trump/Bannon side of the Party -- are deeply humiliated that Donald Trump is now the standard-bearer for their party.
It's embarrassing that a man whom everyone -- including his closest confidants -- agrees is a complete idiot has become the Republican mascot.
Of course, nobody likes being humiliated. But rather than taking aim at the actual root problem -- that they're Republicans in a world where Donald Trump is the Republican Party -- they're instead lashing out against those figures who are keeping Trump's mendacity and incompetence in the public eye.
This is how we get Senators Grassley and Graham -- often thought of as members of the "responsible" GOP wing -- requesting a criminal investigation of the author of the Steele Dossier. This is how we get Speaker Paul Ryan backing Trump water-carrier Rep. Devin Nunes over the Department of Justice regarding access to classified documents in the Russia probe (Nunes recused himself from that investigation after being accused of disclosing classified information; the House Ethics Committee cleared him last month). We see it in the ongoing efforts to discredit virtually our entire law enforcement apparatus as it continues to zero in on Trump administration malfeasance. We see it in the flatly incredible pivot back to LOOK AT HILLARY'S EMAILS in a last-ditch attempt to deflect attention.
They know that they're in bed with a bad guy. I have no doubt they find it deeply shameful. But instead of manning up and actually working to extract themselves from the situation, they're instead more upset that everyone keeps on talking about it. What they want is to return to a state of blissful -- if not ignorance, than at least quiescence -- where Trump's obvious deficiencies can be laughed off as within the bounds of normal politics, and they can just pass tax cuts and gut health care without having constant whispers of "is the Republican Party fiddling while American burns" hovering in the background.
It won't work, of course. It isn't Comey, or Mueller, or Rosenstein, or the FBI, or the DOJ, or the mainstream media, that is the root of their humiliation. It all boils down to the fact that they're Republicans in a period where Donald Trump has ascended to the fore of the Republican Party. So long as Trump is still in charge and still a Republican in good standing, he will continue to do things that will humiliate other members of his party.
The only question is how much damage the so-called "responsible" Republicans will do in their desperate attempt to avoid responsibility and pretend like if they close their (and everyone else's) eyes, this will all go away.