Understanding the political success of U.S. President-elect Donald Trump is not easy. There have been many glib comparisons with populist politicians of the past, from Huey Long to George Wallace. But the most revealing comparison may be with a historical figure from another country: the British nativist firebrand Enoch Powell in the late 1960s and early 1970s.

At first glance, the comparison might seem peculiar. Powell came from a lower-middle-class family. He was a classical scholar of true erudition and a man of principle. He was also a political insider, having served in Parliament since 1950 and as the junior minister for housing in Prime Minister Anthony Eden's government in 1955.

Still, the parallels with Trump are undeniable. In his notorious 1968 "Rivers of Blood" speech, Powell, a skilled orator, broke decisively with the political mainstream. He decried immigration and denounced the Race Relations Act of 1968, which prohibited discrimination in housing, employment and lending. The passage giving his controversial speech its name alluded to inner city riots in the United States and invoked Virgil: "Like the Roman, I seem to see 'the River Tiber foaming with much blood.' "