The SCOTUS un-decision won’t matter nearly as much as whether people can go visit family on vacations. For example, my niece and her husband are fairly conservative. They live in Texas. Their parents live in Colorado and Wyoming, respectively, and visit often to see the grandchildren. If Texas secedes and there are border issues (as I expect there would be), they might not be able to see family when they want to. THAT will be first and foremost in their minds if/when they are asked to vote about secession.
We make the assumption that most people think politically. They do not. They think about economics and family. They don’t see Democrat vs. Republican as much as they see about jobs, family and friends. Putting up borders between people is the “hard sell” I’m referring to.