It's easy, just go against what he said during campaign. He promised "law and order" (code for no immigration), "radical Islamic terrorism" (code for no Muslims in US and kill them outside US), "beautiful coal" (code for jobs for uneducated), and "Merry Christmas" (code for owning the liberals). All other activities, from tax breaks to Iran deal, are others getting their agenda taken care of. He is doing well according to him, though he doesn't know how incompetent he is in getting his stuff done. By fighting for wall, loosening the criteria for drone attacks and implementing Muslim ban, removing regulations, and praising MAGA hat wearing/torch wielding people, he thinks he doing an A+ job.
And his followers love it. They clearly see how faithful he is to his promises and any lack of success is purely due to the amount of obstacles from fake media, Democrats, and liberal deep state. Form their point of view, the issue is crystal clear. The only way Trump will lose his followers is if he abandons the promises he campaigned on (and not silly fantasies like turning democrat).