Donald Trump is one of the most extreme presidential candidates to gain widespread support in contemporary American politics. Despite championing policies like the end of birthright citizenship, mass deportation of undocumented immigrants, and a registry of Muslims living in the United States, Trump has consistently polled atop the Republican field since July. A popular perspective thus attributes Trump's success to a "right wing fringe" of GOP voters. But this conventional wisdom misses something important: Trump meets the textbook definition of an ideological moderate. Trump has the exact "moderate" qualities that many pundits and political reformers yearn for in politicians: Many...