I am old enough to remember Tip O'Neil has the jolly, towering figure of MA politics, and the peculiar thrill of hearing a very heavy Boston accent open the State of the Union address by announcing: "Mist-ah Speak-ah! The President of the United States!"
Part of the problem of course is that most people don't understand what O'Neil actually meant. Most folks interpret it, as Gelman rightly points out, as being about constituent services and bringing home money. Actually, my feeling based on my vague memory from having read O'Neil's memoirs 25 years ago is that he meant you need to actually stay in touch with your constituents, listen to them, and make them feel listened to. That's not pandering to them, that's respecting them, which is something O'Neil actually did and most others do not.
Of course, the world was extremely different in O'Neil's day. But it was different not merely in the level of partisanship (which waxes and wanes) but in the level of a critically important input that doesn't exist much anymore -- local news. Combine this absence with the fact that these days member spend more time out of district, and more time in district doing direct fundraising, and there is no longer any information for voters to distinguish between national and local issues.
Because "all politics is local" only works when the citizenry feels informed on local issues and actually stays engaged out of sense of responsibility at the personal/local level rather than on a "team" basis. But this is only possible if you actually have any sense of how decisions made nationally impact locally and where your specific interests (or the interests of the country as a whole, if you are so inclined) lie with regard to this set of interactions.
The death of local news means local politicians don't explain why certain policies, whether favored by the party or not, are "good for [your state's name here]" except in the most generic way. At which point, it is not about nuance, but very broad strokes of philosophy. It is also a function of local politicians spending less time in the district and more time at fundraisers. Tip walked the streets of Cambridge. He did not need pollsters and focus groups to explain to him emerging trends-- he saw them by walking around. He read them in the Globe and listened to the news on Channel 4 or 5 or 7 at 6 p.m. (before the national news) and then at 11. He also didn't convene "Town Meetings" to explain his policies and give folks five minutes at a microphone. He showed up at events and talked to people about what he was doing.
When all news is national, all elections are national. How can it be otherwise? When elected officials feel to people like remote politicians rather than local people, how can it be otherwise? In such an environment, it is about picking a team.