If you're expecting to convince people, it sounds like you're putting in the wrong effort. The goal of a conversation is understanding, not agreement.
"Here, let us rationally discuss the issues, but regardless of what you say I'm going to go back and vote for [their candidate]" is exactly how a conversation ought to go. If your expectation is different, it's not them. It's you.
If I fly to Japan, my goal is to understand Japanese culture. My goal isn't to Americanize it. And vice-versa. It's no different here. You're not going to successfully impose your values on other people.
"If you know the enemy and know yourself, you need not fear the results of a hundred battles" - Sun Tzu