No one “serves” the President – you only “serve” monarchs or dictators.
The presidency is an office, not a person, and “loyalty” (if any) is only due to that office, not to a specific person.
The President is not the highest power in the land – the people are. All government authority in this country derives from the people. (“We the people…”)
The President is not even the highest authority in government – he is explicitly answerable to Congress (through the process of impeachment), and no amount of crying “executive privilege” is going to change this fact.
The President isn’t really meant to be a leader, he’s meant to be an administrator – his duty is to faithfully execute the laws that Congress passes with the money Congress grants. In this way, the President kind of serves Congress (which itself serves the people) – and not the other way around. (And this is how it should be – unless you personally enjoy dictatorships.)
The President is only really a “leader” of his own party, and only has “authority” that his party grants him, through their control (or lack thereof) of Congress.
If you want to think of it as a business (which it is not, but for the sake of argument we’ll make the comparison), the President is the CEO, Congress is the Board of Directors, and the people are the shareholders. A CEO may be “in charge” of the company, but he’s answerable to the board, and needs the board’s approval for major decisions. And if a CEO does things that decrease the value of the company and hurt the shareholders, he – along with the board of directors, if they went along with it – is going to rightfully find himself in very hot water with some very angry shareholders.
Oh, and the President absolutely cannot pardon himself. That is the logic of a 5 year old.