Majority of Americans think there should be a third party

[angus]

Since 2007 there has been consistent high support for establishing a third party - its 58% in a new poll. Greens, various conservative alternatives and Libertarians get little support, and noone seems able to create a viable Social Democratic party like NDP in Canada, but is it possible to create a viable centrist reform party between Dems and Pubs?

Is it just frustration when voters say they want a third party, or would they actually like a (moderate) alternative?

http://dailycaller.com/2014/09/24/poll-58-percent-of-americans-want-a-third-political-party/

I agree that more alternatives might be attractive, but it won't happen.  Not because the Greens are naive tree huggers or because the Libertarians are stoners and gun-nuts.  It's just that our electoral system is set up to favor the evolution of a two-party system.  It doesn't have to be the Democrats and the Republicans, and I suspect that from time to time over very long-range cycles there will be upheavals, but two strong parties will always come out on top.  You'd have to remodel the US constitution to change that.

In political science studies, this phenomenon was formerly known as Duverger's Law, after Maurice Duverger who published a major study in 1955.  Unfortunately, Duverger's study was very general and it doesn't really adequately explain the peculiarity of the US "winner take all" system.  The history learning site does a pretty good job trying to explain it in layman's terms, and you can use Google Scholar to come up with more detailed, peer-reviewed historical explanations specific to the US system.

While I freely admit to voting for third-party candidates from time to time, I also have to admit that I'm comfortable with a two-party system, especially when I compare the alternative, a one party system.  Egypt before the Arab Spring or Germany in 1940 or modern-day China don't appeal much to me.  If Americans really want a multiparty system, then they're going to have to revamp the constitution.  I don't think there's much appetite for that, despite claims that it would be nice to have alternatives to the Democrats and Republicans.

[angus]

It would be better for libertarians/true leftists/moderate heroes to hijack one of the established major parties.

I think it's actually the other way around.  When a minor party comes up with a good idea, and they sometimes do, the Democrats or Republicans co-opt that idea and make it part of their platform. 

[angus]

The electorate is polarised. The parties are streamlining because that is the pressure from voters.

There's that too.  Good point.  The polarization is fed by successful marketing strategies, of course.  I hate them because the talking heads I watch hate them, and the talking heads I watch hate them because they have read in the polls that I hate them.  Vicious cycle.

[angus]

new parties ... are hard to establish and would likely marginalize one of the existing two if they became successful.

yes.

Didn't realize that you were a history and politics major.  I'm sure you understand all this better than I.  I was a believer in strengthening the minor parties at the expense of the two big ones for a long time, but I guess I'm more skeptical about all that as I grow older.  Certainly the founding documents, of which we are rightly very proud, constrain our democracy in unfortunate ways.