I know Heath and his family. His positions are very conservative on most issues but his family is overwhelmingly old south Democrats. I once heard a likeminded in law of mine say seriously that he hoped God would forgive anyone who voted for a Republican. It would have been very difficult for him to have run as a Republican.
They're part of the last hold outs still voting the Civil War.
The Dem brand hurts Heath but many people who care about him won't vote for him next time because he supported Pelosi for Speaker. Liberal leadership in the House insures that the issues Heath says he cares about will never see the light of day.