Well look at it in this light, being president is a hard fucking job. I mean have you seen the before and after pics of bush? It takes its toll. I can only imagine what it must have been like for FDR in his 16 years of presidency. Some presidents have been known to go a tad crazy, not really crazy but just a little bit. So it could be that getting elected that second time, after a bit into it you just start to not care about so many little things, especially if you have a crazy thing like a war going on. Two wars even. But look at these scandals shall we?
Clinton and lewinsky: Well considering clinton was a mini kennedy I cant say Im surprised, it kinda falls into what I was saying and it kinda doesnt seeing as he was like this all the time.
Reagan and Iran Contra: This isnt a scandal so much as a shit storm trying to be averted. We were trying to build relations with Iran AND save hostages. Unfortunately Iranians are... how to say evil nicely. xD Well they arent evil but they sure know how to fuck up a good thing. So it cant fall into what I was saying because it wasnt reagan that caused or did this, it was just a response to events going down in the world.
Nixon and watergate: This is perfect for what I was saying. In all fairness though, wouldnt you want to know what your rivals were up to?
The reason I skipped over bush is not because you named alot, its because they stem from the war
(except katrina, despite popular belief she is not related to al queda(?)) and are more a direct response to it then bush. Really, I dont think bush fucked up then couldnt get a hand hold. Starting off with 9/11 and a war really fucks up your balance.