If people are content, safe, and prosperous they will vote for the incumbent.
If people are unemployed, starving, scared, or even uncomfortable, they vote for change.
I'm not talking about the base of either party - they've already decided who they will vote for. I'm talking about the mushy middle. If you get them to vote for you along with your base, you win.
It's really not that complicated.
You’re right. Sadly.