For some reason that I don't recall, I looked at Edward Banfield's The Unheavenly City Revisited (1974) the other day and ran across this passage, about what he thought was an increasing influence of the middle and upper classes in political life:
"The upper-class ideal . . . requires that issues be settled on their merits, not by logrolling, and that their merits be conceived of in terms of general moral principles that may not, under any circumstances, be compromised. In the smoke-filled room, it was party loyalty and private interests that mainly moved men; these motives always permitted 'doing business.' In the talk-filled room, righteous indignation is the main motive, and therefore the longer the talk continues, the clearer it becomes to each side that the other must either be shouted down or knocked down."
Except for the "knocked down," this seems like a good description of the direction of change in American politics since the time he wrote. On the other hand, there is an argument, backed by a good deal of evidence, that increasing levels of education promote stable democracy: education increases openness to new ideas and ability to see the other person's point of view (see this article for references and more discussion). So it doesn't seem that Banfield's hypothesis could work as a general rule, but maybe it applies under some circumstances. One obvious possibility is that the effect of education changes directions--up to a point, increases lead to more willingness to compromise, but beyond that point they reduce it. There's no systematic evidence of this at the individual level, but it fits with some claims about the politics of intellectuals (see the article referenced above). Another possibility, which I think is more likely, is that there is some kind of interaction between social conditions and the political system. That is very vague, but it seems worth thinking about.