If out-group hostility is more important to party identification than support for particular policies or ideologies, we may not actually place very many ideological demands on our parties. Defeating our enemies may be more important than advancing specific liberal or conservative agendas. According to Groenendyk: “If partisans’ identities are increasingly anchored to hatred of the outparty than affection for their inparty, electoral dynamics are likely much more fluid than many accounts suggest. Thus, insurgent candidates with questionable ideological credentials (e.g., Donald Trump) may be more appealing than one might expect in the age of ideologically sorted parties.”

Source: America’s Polarization Has Nothing To Do With Ideology | The American Conservative