Graham and Trump had a telephone conference a couple of days ago, so it’s possible that this was coordinated in case witnesses were called and that Graham’s vote was a strategic vote. I believe this gives him the right to intervene in the process in some way.
I suspect Graham may have changed his vote in consideration of parliamentary procedure, Senate Rule 13. In order to preserve ability to move for reconsideration of the vote for hearing witnesses, a senator must have voted with the prevailing side, or not voted.
https://www.govinfo.gov/content/pkg/SMAN-116/pdf/SMAN-116.pdf
RULE XIII 13RECONSIDERATION
13.1
1. When a question has been decided by the Senate, any Senator voting with the prevailing side or who has not voted may, on the same day or on either of the next two days of actual session thereafter, move a reconsideration; and if the Senate shall refuse to reconsider such a motion entered, or if such a motion is withdrawn by leave of the Senate, or if upon reconsideration the Senate shall affirm its first decision, no further motion to reconsider shall be in order unless by unanimous consent. Every motion to reconsider shall be decided by a majority vote, and may be laid on the table without affecting the question in reference to which the same is made, which shall be a final disposition of the motion.
213.2
When a bill, resolution, report, amendment, order, or message, upon which a vote has been taken, shall have gone out of the possession of the Senate and been communicated to the House of Representatives, the motion to reconsider shall be accompanied by a motion to request the House to return the same; which last motion shall be acted upon immediately, and without debate, and if determined in the negative shall be a final disposition of the motion to reconsider.
Yes, I think you’re right. Graham does know procedure.
Thank you kindly.