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It's an empirical generalization rather than an analytic abstraction, and might be idealist as much empiricism is. But it is also a position widely held. I picked up the exact phrase, "go to die," from an aside in an article in London Review of Books some years ago -- where it referred to the fate of the populist movement in the late 19th-c.
"Revolutionary" parties _can_, of course, play the same role. I have suggested that the Party we need will be much like the SPD of Kautsky, Luxemburg, Bernstein, et al. That was a revolutionary party, but it also was a place for the likes of Bernstein. Probably, as I've suggested before (following an argument of Andre Gorz) that a mass working-class movement has to achieve most of its goals within about a 5-year framework, and then (for reasons Charles Post has outlined) tends to subside.
Carrol