Robert W. Merry is editor of The National Interest and the author of books on American history and foreign policy. His next book, Where They Stand: The American Presidents in the Eyes of Voters and Historians, is due out on June 26 from Simon & Schuster.

Thomas Hart Benton was one of the greatest U.S. senators who ever lived. He represented Missouri from the moment it joined the Union in 1821 and then held sway over his state’s politics for thirty years. He was a man given to flights of outrage that unleashed torrents of outrageous rhetoric. An imposing man with a big face, full of crags, and a beak of a nose, he spoke with authority and an air suggesting he didn’t have much patience for the mutterings of lesser men, a category that seemed to include most of those with whom he came into contact....

Thomas Hart Benton’s political fate comes to mind in the wake of what happened this week to Indiana’s senator Richard Lugar, defeated in his party’s primary after loyally representing his state in the Senate for thirty-six years. Temperamentally, Lugar was nearly the opposite of Benton. The Indiana senator’s style is self-effacing, low-key, given to quietly amassing vast stores of knowledge on complex issues often little understood by the public. But, like Benton, he accumulated immense power in the Senate over many years and served his state precisely as it wished to be served.

When such men are cast aside, it serves as a good occasion to ponder those vagaries of democratic politics that can operate with such unsentimental force and deal so harshly with people who only a short time before were considered part of the nation’s political landscape. Such a man was Lugar, as was Benton....