It's possible the Kavanaugh vote ends up benefiting her politically-she may not have been able to be renominated if she had voted against and been responsible for stopping both Obamacare repeal and the Kavanaugh nomination, and she may have enough of a positive image with moderates and Maine may be close enough to a swing state to make the damage she takes with the general electorate for the Kavanaugh vote survivable. I hope that she is proven wrong here, but Collins probably only needs to outrun Trump by a few points to win.
Yeah it's kind of bizarre how so many of the red avatars here seem to think Maine is Massachusetts. Collins losing most of her crossover support from Democrats would've been a death sentence in 2008. In 2020 it is an obstacle, but far from an insurmountable one.