Americans love to hate Congress, and no wonder given the careerists and poseurs in both parties. But some Congresses matter more than others, and the 115th has accomplished more useful conservative reform than any since the first Newt Gingrich years of 1995-1996.

Democrats won’t admit it for partisan reasons, and neither will some of the perpetually angry on the right. But the GOP’s narrow Senate majority of 52 seats and then 51 has turned out to be more consequential and conservative than the 55-seat GOP majority of 2005-2006,...