Historically the public has blamed Republicans for shutting down the government when Republicans shut down the government. The divide in the caucus is between those Republicans in safe districts who have to be extremist in order to avoid getting primaried and those Republicans in competitive districts who might lose their seat in the general if the public blames the GOP for the shutdown. The Democrats mostly just have to message that they will take a reasonable deal to avoid the shutdown and let the rest be McCarthy's problem.