Historical anecdote of the day, summarized from Geoffrey Kabaservice’s highly-recommended Rule and Ruin:
Donald Rumsfeld began his career as a moderate, reform-minded congressman, during which he made friends with a liberal anti-war Democrat named Allard Lowenstein. The two were so close that when Lowenstein’s GOP opponent in the 1970 election started red-baiting him, Rumsfeld came to his defense—a rare moment of party-crossing, even then. The local Republican Party complained to the Nixon administration, which ordered Rumsfeld to fall in line and denounce Lowenstein, leaving our hero with a dilemma: stand up for his friend, or throw him under the bus for the party.
He chose the latter. Lowenstein never spoke to Rumfeld again, and Robert Novak said the candidate was more shattered by the betrayal than by losing the election. Quoting Kabaservice: “Rumsfeld would go on to be one of the most durable and accomplished Republicans of his generation, but at the price of becoming one of Nixon’s tough men of the center, unencumbered by excessive human sentiment.” That’s one way to put it, I guess.