They could be protecting their asses, sensing that there's something to this whistleblower complaint, and it should have, by law, been given to the Congress seven days after it was either lodged or had a judgment made by the IG, which in this case was extremely urgent.

With a few exceptions, whatever they do they will do in unison, until they are called upon to convict an impeached President.  If he is impeached, and the reasons are overwhelming, and determined to have been covered up by both the White House and the Senate, Mitch McConnell will be hard put to explain the  Senate's gutless performance this past year and nine months, while he is gathering up the troops to convict.

He may ride it out and recommend not to convict.  That's where you will see the true patriots, men like Romney  parting ways.

Getting the President's permission to deliver the transcript plus, now, the full complaint puzzled me.  Until I remembered his campaign boast that he could shoot someone on 5th Avenue and not lose a vote.

Perhaps he has deluded himself into thinking the same holds true for what he know is an impeachable offense.