ND, he has never been elected to anything, but to use your words, I'm not concerned with ancient history, I am concerned with 2016, a year during which he is *running* for something, and that something happens to be President of the United Fucking States. He can bring corruption from his life into office without having been a politician, and he will.
He cannot run his companies any way he wants, just as I cannot run my company any way I want. I cannot evade taxes for decades. I cannot start fraudulent businesses that rob people of their life savings. I cannot stiff clients out of the pay I owe them. He can't do any of those things either, but lo and behold, he has a lot of money moving in and out that he can mooch from when he needs one of the world's best lawyers, so despite the fact that he can't, he runs his businesses any way he pleases. It is immoral at best and illegal at worst.
When Clinton, Bush, or Obama do something wrong, you are exactly right. When Donald Trump does something wrong as things are today, he makes a lot of noise on TV and a few people get screwed. As President, if he does something wrong, then he faces the exact same consequences as Clinton, Bush, or Obama. Do you underestimate his power while harping on the power that past POTUSes have had? Do you think his power would be any less? He isn't just "one person in the private sector" as President.