Former President Donald Trump could be heading for a much worse performance in November than his poll numbers suggest if, as most experts suspect, he continues winning primaries and takes the GOP nomination again, Republican focus grouper Sarah Longwell told MSNBC’s Chris Hayes on Wednesday’s edition of “All In.” There are two main reasons why Trump is facing a huge hidden liability, she argued — and both have to do with the fact that voters aren’t yet truly processing what a Trump rematch actually means. “My hypothesis here, and I think there’s a lot of evidence for it, is that as soon as vot…