I'm not sure that has changed that much. There's always been a component of politics that's tribal in nature, and it takes a lot to overcome that inertia. It's not unlike sports, where people will root for the local team, even though there's not much that's local about the team other than the name.

You can see that behavior for example around the ACA. It's obviously inspired by Mitt Romney's Massachusetts health care reform, so you'd think the Republicans would be all in favor of it. Yet at the federal level, since it was pitched by the Democrats, the Republicans are against it.