Romney has already said that it is a “lie” that he will not confirm whoever President Trump nominates. All the weasels you mention are running scared, along with a Democrat or two. McConnel and Co. have been on a Ruthy death watch for years. They are ready for this one. Mitch knows he has the votes or he wouldn't have said that he would get President Trump's nominee confirmed. He has already gotten over 200 of President Trump's nominees confirmed. He feels that this is his legacy.
This is McSally’s chance to attack the astronaut as a gun-grabber. She must vote for POTUS’s (presumably pro-2A) nominee before the election, and make it a decisive issue to get back in that race.