If they can get the bulk 'anonymized' data, there's a high chance they'll be able to identify the individuals. Anonymized data is such a joke that it rarely hides the identity. For example, if you have cell phone GPS data, the name of the owner and the phone number can be hidden, but if it starts and ends at the same place every day, then you can figure out who it is.
In browsing habits, you might look for people who surf to the congressional mail server web page. You might search URL query strings for embedded names. There's a lot of potential there, and the anonymized data might even include their address, which happens sometimes when the vendor doesn't actually care about hiding identity.