What I know after living through 4 years of Trump:
At least half the voters don't really care about the issues, the public good, or the bigger picture. They specifically don't choose their candidates based on logic. They support people who normalize their base qualities. It's an emotional response, not an intellectual one.
That's why you can talk until you are blue in the face, present all the "facts" and "proof" in the world, and they will not listen. You can't convince people like this because they make decisions based on their belief system, not with their logical mind.
So how do you change their stance, their views? You present something that grabs them by the heart - challenging their belief system. Be prepared for anger, though. Belief systems are murky and primordial.
Consider Boris Johnson. He recently turned off a lot of his avid supporters by being caught doing something as simple as going to a party during COVID shutdown, after telling everyone else to stay home.
It's a bit more complicated in the U.S., where Trump would never tell people to stay home or mask up, but I did notice that he was booed at one of his ridiculous "rallies" recently for telling his supporters to get vaccinated.
Many thanks to Steve at Shadows & Light for making me think about Boris this morning.