Republicans have spent the last year cutting taxes and regulations, which hasn’t been easy. But now some Members of Congress want to blunt their handiwork by passing an online sales tax. Yes, they actually believe this would be good policy and politics.

A large faction of House Republicans are pressing GOP leaders to attach legislation to the omnibus spending bill that would let states collect sales tax from remote online retailers. South Dakota Rep. Kristi Noem’s legislation, which has 50 co-sponsors, would let some 12,000...