If Palin would announce that if Murkowski votes no she will begin a vigorous write-in campaign against her. She would probably even win but even if she didn’t she would ensure Murkowski’s loss. McConnell should also promise Collins the moon for a yes vote and when he does not keep his promises to her afterwards it will be just a shame.
Murkowski doesn’t come up again until 2022, I believe, and AK people like these kind of “mavericks”.