-PJ
If they force Johnson out to make cloture easier, then they are faced with a Republican governor in South Dakota who would likely replace him with a Republican, giving majority votes to Republicans (but not control). Then, the Democrats would try to force Republicans to appoint a Democrat to replace Johnson out of fairness, because the Democrat governor of Wyoming is replacing Thomas with another Republican, even if it's only because he's required by Wyoming law to do so, and not out of a sense of Democrat fairness to Republicans.
None of this will really happen, I'm just speculating on possibilities.
-PJ