Sasse would love to defect to the dark side Democrats but realizes that he can never win reelection and that he would always be rightly viewed as a traitor by all. Another Flake. A majority of 56/44 in the Senate would make him irrelevant.
...but realizes that he can never win reelection...
Which should only be a one-time concern for any of them...TERM LIMITS, NOW AND FOREVER! Serve your two terms then go back and live under the laws you passed.