It's probably worth also noting that one of the things going on here is that the internet really has changed things a bit. Back when Richard Fenno was doing his original research in the 1970s, Members of Congress could pretty much say anything they wanted back in the districts and no one in Washington would ever know. There were no videos available of Members in their districts; there were no local bloggers. Not only that, but there was essentially no way for ordinary people in Washington to read stories that were reported by local reporters for local papers. The only real way things could be transmitted would have been if the story got picked up by a wire service and then run in a Washington paper, but that wasn't going to happen. Sure, every once in a while a David Broder could go out into the country to report on what was going on, but all of the national reporters who did that put together might have managed to cover a dozen or two appearances by all Members combined.
Information flows in the other direction as well. I suspect that the current Senate Finance markup is featuring the most scrutinized committee legislative votes in Congressional history (various nomination votes, especially Supreme Court votes, and the July 1974 actions of the House Judiciary Committee, were more scrutinized, but I can't think of any others).
If I were evaluating Members of Congress for partisan loyalty, I'd pay a whole lot more attention to the second of these sources of information (actual votes) than the first one (what they say in the district).