From a Washington Post story, titled "As Trump ranted and rambled in Phoenix, his crowd slowly thinned":
Hundreds left early, while others plopped down on the ground, scrolled through their social media feeds or started up a conversation with their neighbors…. [T]he president just wasn't keeping their attention…. [H]is rage seemed to cloud his senses….
The president … tried to connect [his] lengthy self-examination to his supporters. Meanwhile, a growing number of them were calling it a night and heading to the exits.
I suspect the fanatical core of true Trumpeteers is somewhere in the percentage range of those who believe it's socially acceptable to hold murderous neo-Nazi and Bannonesque white-nationalist views: about 9 percent. The others are just run-of-the-mill imbeciles who know nothing of American government and are thus tenuously attracted to bloviating ignorance. By next year or the year after they'll move on to yet other Republican pols, who, in keen competition with Sandersites, are battling to monopolize populist ignorance.