Before there can be Left party, there has to be a class base for the Left.
Take the example of the Green Party, probably the largest left party in the U.S. at present.The problem with the Green Party, aside from the usual problems that plague all third parties, is that it’s a matter of putting the cart before the horse. During the 1950s and 60s, the working class was rather successfully integrated into the middle class due to rising living standards, technological changes, labor power, and political reforms. Then the working class got lazy and failed to protect its position (largely part due to its co-optation by social conservatives with appeals to patriotism, race, crime, “traditional values,” etc). Meanwhile the cultural left took over the Left.Then the corporatists launched their neoliberal counterattack on the working class, and neither labor nor the Left was capable of resisting. The working “middle” class has since been almost completely hollowed out while the neoliberals have successfully ground the working class down to semi-lumpen status. Meanwhile, the “Left” is merely a haven for middle to upper middle class identity politics, plus every kind of personal pathology yet to be invented (“the personal is political” and all that). That’s why nowadays the main issue driving the entire spectrum of the US “Left”, from the CPUSA to the Trots to the Workers World to the Greens to the Anarchists to the Left-libertarians, is the “LGBTQ” thing. There is no “red and black” Left anymore. There’s only the “pink and green” left which is really no left at all.
I was around the U.S. Greens when they were organizing back in the early 90s, and I knew then they would be a disaster. Mostly they were just bohemians often consumed by white guilt. The formation of a “Left” party today would require a complete psychic sea change. It would have to position itself as an unabashedly lumpenproletarian party (e.g. gangs, militias, ex-cons, etc.) and that means throwing overboard most middle class liberal pieties about race, gender, sexuality, meat eating, guns, sugar, smoking, seat belts, video games, motorcycle helmets, drugs, prostitution, etc. And that’s not going to happen. The “left” today is merely the “left-wing” of the middle class.