I was conflicted at first on this. Being a Dem., I assumed she was kinda slammin Rep's.. But after a quick search, it appears this tradition crosses party lines, as most searches actually revealed her fellow Dem.s do it just as much, if not more, than the other party.
Personally, I couldn't care less. They wanna crash in their office, so be it. I don't care if it's because they work long late hours (or say that's why) or they admit the reality - It's wicked expensive there. The point is, my fellow American's, if they are forced to ditch the office, while we can argue whether it's professional (cuz it's not), the thing is magically BOTH parties will be slapping some pay increases on other bills so they can afford/budget in the necessary monies to rent in the area.
And I will say this - Again, while not a fan of the practice in place here, there are FAR MORE SERIOUS things to worry about than whether someone is asleep in the office overnight or not.