Ideological Factions in the Republican and Democratic Parties

Both the Republican and Democratic parties are internally divided. Each contains a party regular wing, which is interested in winning office and in the compromises necessary to govern. And each contains an ideological wing, which is interested in close adherence to the core coalition of the party. But the nature of the cleavage is very different within the parties. Among Democrats, the cleavage is mild, with most members belonging to the party regular camp, to the chagrin of ideologues, who are for the most part Bernie Sanders supporters. The cleavage among Republicans, though, is so deep that the party could not find a way to bridge it in the so-called invisible primary for 2016, creating an opening for Donald Trump, who is from neither camp.