Nuking the filibuster is unprincipled, but it also makes little political sense: Trump would be doing Democrats a huge favor by greasing the wheels for exploiting fleeting one-party national majorities in the future, which will allow them to shove through massive generational “reforms” without any national consensus. And they would be able to do it without taking any political heat for nuking the filibuster. In recent years, they’ve coalesced around an argument that says the 60-vote threshold to cut off debate in the Senate is antiquated — a “Jim Crow relic,” said one-time filibuster champion former President Barack Obama —...