No politician in their right mind would want to make an "alliance" or dance at Harry's feet. This Harry is loose cannon that is literally only good for killing things. Also, the people cheering for Harry were students who most likely thought that it was just cool magic, not Dark Magic, who the politicians don't really need to pander to. If anything, he might be manipulated by politicians to further their agenda, but not pandered to. Dumbledore is considered the most powerful wizard because of what he achieved. He defeated a Dark Lord, Discovered uses for Dragons Blood, and who knows how many other things. As for Voldemort, we don't really have a clear idea of how many followers he has. Voldemort has also proved his power by proving a challenge even for Dumbledore. Harry is a psychotic nobody student, who displayed how stupid he was by using highly illegal Dark Magics in front of Ministry Officials and showing them that he should have been kept in Azkaban. He's not doing any favors for himself and he's not proving anything to anyone that matter except how desperate to prove his power. He is also not a good representative for Hogwarts or Britain.