The only thing that unites the 40% of voters which constitute right is social conservatism. The right's economic policies are shared by the center-left wing of the Democratic Party for the most part. And it's not difficult to imagine moderates adopting some degree of social conservatism. Hell, they have a history of it- Clinton's don't ask don't tell, Obama's opposition to gay marriage, Biden's entire career of targeting POC with law enforcement, etc. etc. etc.
Really what we need is to jettison FPTP and then we'd have 3 or 4 parties that better reflect the entirety of the political spectrum, or at least do serious reforms of the current system. A minority of the electorate is greatly empowered by the electoral college and this minority is extremely reactionary. We'll always struggle to progress if this group maintains their disproportionate influence.
An actual proportional representation system wouldn't give you what you want, which is a center-left and left-wing party jockeying for control.
The actual reality, as David Shor as pointed out, is we'd get something like this in a multi-party system
Center-right: 30-35%
Center-left: 25-30%
Far-right: 20-25%
Left: 10-12%
Libertarians: 5-10%
Note the center-right party would include many of the current suburban voters in the Midwest and Mid-Atlantic who currently support Democrat's because of social issues and not wanting to be directly allied w/ the crazies. If the crazies were in another party, they'd be far more willing to align with a center-right party led by a Larry Hogan or Charlie Baker, as seen by both Governor's 70%+ approval ratings in those incredibly blue states.
If anything, I think if you actually want a Left-led takeover, PR is actually bad for the Left, at least in America. Remember that PR was originally created by moderate liberals, scared that thanks to FPTP, Socialist's would be able to take control full control of European countries w/ 30-40% of the vote.
The actual reasons we never had a Labor/Socialist/etc. party in America, putting aside the obvious race issues is two-fold - the Electoral College (since that just amplifies the WTA nature of things), and the size of our districts. In the UK, a third party can gain popularity because the average district size is about 70,000, as opposed to 500,000 to 700,000 in the United States.
The 40% of the country that are social and racial reactionaries will have a vote, no matter the system we have. Obviously, we should get rid of the Electoral College, and move to some form of STV, PR, RCV, but because it's more democratic, not because it'll lead to a world where the Left wins all the time.
Don't you think the party is somewhat responsible for leading some of those people there via their direct rhetoric and media arms?
I mean, the country being 30-35% basically reactionaries has been true for a long time now. It's just it used to be they were split between right-wing Birchers talking about Communist's in the shadows, and segregationists railing against the Negro in two separate parties, so the more moderate aspects of both coalitions could work around them. Which was bad for other reasons (aka - race issues being depressed), but also meant the reactionaries didn't realize their electoral power.
Obviously, Fox News & such is responsible for some of the specific nature of the radicalization, but I'm old enough to remember when Rush Limbaugh had a national syndicated TV show where he openly mused about a Clinton Body Count.
