Partisan. 100% partisan.
Republican and Democratic rhetoric, for most of the 20th century, was about economic policy with social policy thrown in. Mostly, political parties were aligned based on what we thought we should do with our money.
Then LBJ passed civil rights and pissed off the Southern Democrats enough for them to become the Dixiecrats. Then Lee Atwater and crew discovered that there were racist votes up for grabs and said "we hate darkies, too! Come fly your flags, rebs!" and all of a sudden the divide was social as well as economic.
In order to get the numbers, the economic Republicans have to throw sops to the social Republicans and as the Democrats have moved right, the Republicans have had to dig deeper and deeper into the social bag to keep up their membership. The biggest threat to moderate Repubicans isn't Democrats, it's the Tea Party. It's the Freedom Caucus. Republicans don't fear Democrats. They fear primary challengers. And the primary challengers are winner-take-all.
When George Will drops his Republican Party membership, the ideological heart of the party is gone.