The alt right/populists turned politics basically into a game of us vs them where you associate with "your" party like you would with a sports team. If you say something against "their" party, they take it personally just like saying something bad about their favourite sports team. If "their" party screws up they are way more lenient, like they would be if their favourite does a foul. They win and lose with "their" party and make their personal success dependent on it. That might not be rational but it's normal behaviour for human to associate with groups like that. It just shouldn't happen with politicians and political parties.