While Republicans are thrilled by Donald Trump’s solid victory in the presidential contest and delighted about their new Senate majority, the fulfillment of their most avaricious dreams depends on maintaining control of the U.S. House. That’s because a House–Senate–White House trifecta will enormously streamline the legislative process compared to the constant tug-of-war and messaging battles associated with divided government. It will also unlock the magic powers of budget reconciliation...