John Wesley on 2 Samuel 2:4

Anointed - This they did upon just grounds, because not only the kingdom was promised to that tribe, but David was designed and anointed by God, whose will both they and all Israel were obliged to obey. And they resolved not to neglect their duty, though they saw the other tribes would. Yet their modesty is observable, they make him king of Judah only, and not of all Israel. And therefore there was need of a third anointing to the kingdom over all Israel, which he had chap.5:3, that first anointing; 1Sam 16:13, was only a designation of the person who should be king, but not an actual inauguration of him to the kingdom.