In 2011, Michael B. Brennan, then a lawyer in Milwaukee, vigorously defended the right of Wisconsin’s Republican senator to single-handedly block an Obama administration nominee for a federal bench seat in the state. Last week, Mr. Brennan was confirmed as a Trump administration nominee to that very same seat despite vigorous objections by the state’s Democratic senator.

That incongruity is at the heart of what is fast becoming one of the most significant questions on Capitol Hill: How far will Republican senators go in pushing through President Trump’s judicial nominees over the objections of Democrats from states where the potential new judges will preside?

The answer: pretty far.