It seems like even personally identifying as conservative or liberal is a fairly new (last 30 years) change. Time was it meant "stay the course" vs "shake things up", which are reasonable things the change your mind about from election to election, or federal vs state elections. Now the parties are just sports teams, and you support your side as a matter of personal pride.

Look at Reagan's last election - he was hugely popular, and won by a massive margin in the electoral and popular votes. A big chunk of the country was happy voting for a democrat before Reagan, and went back to voting for one after him. I can't imagine a scenario like that these days.