Good idea. It tracks with my experience working on the Hill years ago, too -- business casual (maybe with a tie) was fine in the House & Senate office buildings, but if you were going to the Capitol, you put on a suit.
True story: I worked for a while in the office of a Midwestern Senator who felt very strongly about this rule. He'd actually fired people in the past over it, apparently. But at one point my boss (his communications director) needed someone to help with a press conference he was holding in the Capitol, and I, who was not wearing a suit, was the only one available. My boss decided I would do because the Senator wasn't going to be at this particular press conference, so he'd never know. So off we go to the Capitol.
Then, halfway through the press conference, the Senator ambles into the room, unannounced and unexpected. My boss' faces turns white as he realizes that if the Senator realizes I'm from his office -- I was too far down the totem pole for him to recognize me immediately, thank God -- we're both screwed. So to protect us both, he does the only thing he can do: he physically grabs me, pushes me into a wiring closet, and closes the door.
This was surprising, but at least I was smart enough to stay in there and keep quiet until he opened the door and let me know the coast was clear...