> That's not necessarily true.

What's not necessarily true?

> Proportional representation often has the undesirable side effect of dramatically increasing the power of small minority parties. The reason is that in order to gain majority control of the government larger parties often have to make significant concessions to a smaller minority party to get the votes.

To the extent that's an effect of PR, its mostly an effect of PR in a parliamentary system, where one needs a stable majority in the main house of the national legislature to establish a government administration.

If you keep the structure of the US government but change the electoral system for the Congress to one which produces more proportional responses, you don't have the same degree of incentive for disproportionate concessions to a minor party to form an administration.

> Two party systems have it's flaws, but what we are seeing now is more typical of a proportional system.

Er, no, dysfunction caused by extremism in the activist base which has disproportionate influence over one or both of the major parties is pretty typical of a two-party system, not a proportional system, as in a system which structurally can support more competitive parties, such extremism will more quickly drive moderates into other (existing or new) parties, and is thereby limited.

> Due to overly effective gerrymandering, the Republican hold on many congressional districts is so secure that the only real threat to those seats is from party extremists.

That's not due to "overly effective gerrymandering" (the fact that Republicans have substantially greater share of House seats than their vote share may be, but there is pretty much no way to divide up single-member, FPTP districts in the US that isn't going to result in lots of safe seats for both parties -- heck, a lot of Senate seats are similarly safe seats, and they can't be gerrymandered.)

And, in any case, gerrymandering itself is a high-stakes operation that can seriously effect representation only in single-member, FPTP districts, so insofar as the current problem is a result of gerrymandering, it is a direct result of the structure of the electoral system.

> Under our normal two party system with less polarized districts, extremist politicians couldn't win in general elections, but now that so many Republican districts are so secure, the party has essentially been captured by extremists (it's not a stretch to call the Tea Party a third party).

If you look at the history of the US, a national two-party system with extremely polarized districts and often a large number of states each effectively dominated by a single one of the two major parties is the norm, not an exceptional state. Your idea of "our normal two party system" is unconnected to reality.

And, yes, its a stretch to call the Tea Party a third party; since shortly after it became visible on the national stage its support has usually been about equal to that of the Republican Party (sometimes a bit more, and sometimes a bit less) and, more to the point, almost entirely overlapped with that of the Republican Party. The Tea Party is just a new branding for the activist base of the Republican Party.

> In the past, the two party system worked by consensus, the more moderate members of each party would work together to carve out solutions to a problem, and keep in mind, the more moderate party members were typically from contested districts, so they needed to demonstrate leadership and good results to get re-elected.

In the past, the two major parties largely represented different regional interests, but represent the same kind of elites, to the extent that their platforms differed it was more driven by difference in the interests of the capitalist class is different regions rather than ideological differences; this started to break down in the New Deal era in a major ideological realignment of the parties, which wasn't really complete until Clinton's first term. The main drivers for this were probably the labor movement and the reaction against it and the development of mass media which facilitated the development of national ideological communities.

> The Republican 'take no prisoners' strategy can probably be traced back to Gingrich.

Sure, the 1994 Contract with America was a watershed moment of the solidiying ideological alignment of America's two parties.

> We are now seeing a culmination of that strategy, and I think most would agree that it has backfired.

That's what people said after Gingrich did the same thing and "failed". The thing is, it hasn't really failed -- that is, done any worse than not doing it -- either for the interests it served, or for the people who executed it who, even if they lose elected office, will end up in well-paid sinecures in the network of corporate, media, and propaganda/think-tank operations that support the ideological Right. Which is why the "defeats" suffered by Gingrich isn't seen as a defeat -- its only a defeat from a perspective which keeps score by political offices held, not substantive influence exercised.

> If I was in the business of making bold predictions, I think I would bet that the Republican party might get replaced by a new, more moderate party in the next 20 years. More realistically, they are going to shift back to the middle.

Sure, what I'd say that's the most likely case: what we are seeing right now is an extended rear-guard action by a faction that maintains disproportionate influence on government despite its shrinking support; if it doesn't turn around support for its ideology, its either going to be replaced as the dominant faction of a major party, have the major party it is the dominant faction of replaced, or establish a non-democratic regime, and the latter seems like the least likely alternative by far.

But the kind of extended rear-guard action it is fighting is only possible because it this faction is both the activist and funding base of a major party in a two-party system. In a proportional system, it wouldn't be possible.