IMO, smart and having any brain cells functioning is in short supply in DC. Corruption, however, is the norm, ya think?
I think that it's they get to DC and it's all about playing the game, like they had to play the game to get there. What's lacking isn't "smart" it's what they've used their brains for. The lack is of wisdom, perspective, and real problem-solving experience. There's no vision of making the future better.
Since WW2 the only Presidents to have that were Ike, Reagan and Clinton (yeah, Clinton).
I don't think John Kerry is stupid. It's more that throughout his life he's tried too hard to please and his insincerity shows through. Obama and hillary seem just plain self-centered and dumb.
It’s always been that way in his case.