The American people did not give power to congressional Republicans; they took it away from congressional Democrats. Republicans now have an opportunity to prove that they deserve majority status — that they can operate not just as an opposition party, but as responsible leaders who are willing to make hard choices and solve problems. The goals of an ideal economic-growth agenda are simple and well known: a large and thriving private sector and a small government; reduced government spending, which means lower taxes (or at least not higher ones) and smaller deficits; open trade and investment; taxes and regulations that...