Granted that there is a high level of political polarization in the U.S., that the trajectory has been and continues to be toward greater polarization, let's ask some important theoretical questions. Why? What caused this bifurcation? and What is the best way to respond to it? In other words let's talk not just about 'facts' but about about causes and consequences.
In terms of causes, it is a commonplace that the primary source of polarization in American politics has been the sharp, prolonged movement to the right on the part of Republicans. I have commented on this here before. So, it is important to see that polarization is not a 'natural' phenomenon. It reflects a political strategy - and an effective one I might add - on the part of the right. The right in the U.S. has, through its nefarious institutional manipulations over the past three decades, arguably proven itself a disloyal opposition. To the best of my knowledge no one at the Oklahoma confab has so much as thought about this.
In terms of consequences, why should we endorse bi-partisanship? That is a fundamentally anti-democratic response. Here I am persuaded by argument by political theorists who, following Joseph Schumpeter (whose conception of democracy is, despite common caricatures, neither a 'realist' nor 'minimalist'), insist that robust competition is crucial to a healthy democracy. For instance, Ian Shapiro* suggests that competition has two salutary effects: (i) it allows voters to throw out incumbents (known more appropriately as 'the bastards') and (ii) it pressures the opposition to solicit as wide a range of constituencies as they are able. Given these effects, Shapiro suggests quite pointedly:
"If competition for power is the lifeblood of democracy, then the search for bi-partisan consensus ... is really anticompetitive collusion in restraint of democracy. Why is it that people do not challenge legislation that has bi-partisan backing, or other forms of bi-partisan agreement on these grounds? It is far from clear that there are fewer meritorious reasons to break up the Democratic and Republican parties than there are to break up AT&T and Microsoft."
Now the final sentence does not follow; we need not break up any particular party and, insofar as they are essential mechanisms of political coordination, that might be self-defeating. What is wanted is vigilance against bi-partisanship and the sort of collusion it embodies. That said, Shapiro's first two sentences are on the money. And the Oklahoma 'moderates' are preaching an anti-democratic homily.
If political polarization is troubling and bi-partisanship is a self defeating 'remedy' for it, what is to be done? Among the crucial empirical observations about partisan polarization in the U.S. is that it reflects the economic bifurcation (in terms of wealth and income mal-distribution) among the population. Because the poor participate at relatively low levels, and because many recent immigrants remain unnaturalized (hence disenfranchised), the constituency for a real alternative to right-wing policies remains politically inchoate. The solution to political polarization is to attack economic inequality, to resist anti-immigration policies, and so forth. That might, in fact, require Democrats to stop their headlong rush to mimic Republicans and prompt them to seek to forge broader and deeper alliances between constituencies that do not now see one another as allies. But that would require the Dems to be political rather than play the bi-partisan game. What we need is more robust competition.
*Ian Shapiro. 2003. The State of Democratic Theory. Princeton UP; Shapiro's views overlap in various ways with the otherwise disparate arguments made by Richard Posner, Guillermo O'Donnell, and in my own writings with Jack Knight.