It must be hard to admit that your first movie that hit was your only one. He has been going downhill his entire life, why would anyone care about his political pick?
These board as hell celebrities whose career doesn’t keep them busy have nothing better to do to stay in front of a camera. Besides, it looks good on their union record they were out promoting a Democrat candidate.
FYI - Mark and Carrie used to show up to the set(first movie) stoned. Not stoned enough to be unable to do their jobs but enough to have George tell them if they didn't stop and get their act together then he'd fire them.