I try not to engage in mindreading, but I've spent a lot of time trying to diagnose the underlying causes and symptoms of Broderitis. The only consistent thing I've been able to come up with is that such people are incredibly elitist. When they speak of a "national consensus" they speak only of an imagined elite consensus which just happens to align with their own political preferences. The nation is "divided" when it disagrees with them, and "united" when it agrees. Democracy is distasteful to them, as they "know" that the rubes must not really be able to have their say in how their country is run.
The weird state of affairs which this country experienced for much of the 20th century, with a substantial number of moderate Republicans and a Democratic party filled with conservative Dixiecrats, gave an immense amount of power to unelected Washington elites who set about always trying to define this mythical "center." The lack of clear difference between the parties elevated pesonality above policy, and left the dirty details of such things to technocrats.
Hopefully those days are over, no matter how much wankers like Broder and Rodriguez squeal about how awful it is that educated voters get to have their say.