Republican voters did their part. When one accumulates the popular vote for House races across the country, Republicans won by three percentage points—a margin that was once just under five points but narrowed as votes from deep-blue districts trickled in over weeks after Election Day. That kind of turnout for Republicans “would normally translate into GOP gains of 20-30 seats,” according to the Cook Political Report. But Republicans have as of early December netted only eight seats, bringing their total in the House to 220. At most, Republicans will hold 222. In races that seemed to be easy flips, Republicans...