I disagreee. Sinatra did a lot for the democrats and he was alive in the party. His relationship with JFK was not just pimp and friend. He thought and was loyal, but JFK betrayed that on the advice of his staff. Sinatra was not shallow, he was being loyal.
If I remember correctly, Sinatra pulled out but Michael Jackson was the replacement. And I think Trump and Jackson were friends.
How is getting miffed, and changing political parties because the President decided not to come to stay in the new wing in your house...being loyal? Friends don't let things like that affect their relationships, nor cause them to change political alliances.
After JFK bailed on him and stayed at Bing Crosby’s, Sinatra cut Peter Lawford out of his life and the Rat Pack. Lawford was the one who had to tell Frank JFK was not coming.