One should check out the talk of 33c3, where a group of german journalists bought this type of data and deanonymized some users.
Oh, and of course they found and deanonymized some German politicians and their staff.
So while it might not be possible to deanonymize and "expose" all of Congress, if you really tried and got some money to actually buy the data, you will be able to at least deanonymize some of your targets, especially if the data originates from a man-in-the-middle like an ISP and not just some random ad network/tracker.