For anyone with a long memory, much less historical knowledge, the idea that Democrats are currently divided ideologically to an unusual or intractable degree is laughable. Today’s centrist-progressive rift existed to an even more alarming extent when Barack Obama was trying to enact his own legislative agenda. In the Clinton administration, conventional liberal Democratic dissent from the presidential agenda was so sharp and regular that the president often got as much or more support from Republicans than from Democrats for initiatives ranging from trade expansion to welfare reform. Clinton’s “New Democrats” (he had originally campaigned as “a different kind of Democrat”) and their orthodox liberal opponents warred constantly until the effort to impeach the president united them.

Going back further, Jimmy Carter had to head off an ideologically inspired reelection primary challenge from “liberal lion” Ted Kennedy. Divisions between pro-administration and antiwar Democrats during LBJ’s second term led to that president’s forced retirement as he faced an almost certain primary defeat, and a convention so intensely divided that the mayor of the host city was shouting anti-Semitic obscenities at a U.S. senator delivering a nominating speech with the whole world watching.

In 1948, Democrats were so divided that not one but two splinter parties (the Progressives under FDR’s second vice-president Henry Wallace, and the Dixiecrats under then-Governor Strom Thurmond) ran candidates against Harry Truman. And going further back, the 103-ballot 1924 Democratic convention nearly flew apart during a vicious fight over a platform plank (which was defeated) condemning the Ku Klux Klan.