lenin's critique of the second international was that it took the tactic of parliamentarism and turned it into an end in itself. over time, as they kept being reelected and made friends w/ their supposed class enemies and got comfortable, they lost their bite and became all bark

it's still true today. leftists who choose to tactically adopt parliamentarism as the most effective route to power may begin with both bark and bite, but over time, as they become acclimated to the system as they rise in it, they lose the latter and only keep the former. if that

unfortunately that's the most important lesson from the failures of the bernie and corbyn projects which no one is willing to admit. instead they're looking for the next person who seems like they might have the personal fortitude to resist. sorry. you're not going to find them

that doesn't mean, as lenin understood all too well (see his critique of the "infantile disorder") that there's an alternative to tactical parliamentarism as the most effective path to power in certain contexts. I guess the only thing you can do is be aware of its limitations

it's not just in politics either, it's a general sociological truism, which marx already observed when he noted that "social being determines consciousness". figuring out ways to maintain fidelity to class politics has long been a mainstay of socialist and communist thought

marx and engels tried the workerist route, setting up rules for a certain amount of members of communist orgs and its leadership having to be proletarians. but it was in tension w/ their own class background and wasn't really feasible as intellectuals became prominent as leaders

kautsky, the "pope of marxism" in the second international period, completed the move away from that by arguing that class consciousness is introduced to the working class "from without", by said intellectuals. lenin sort of agreed, but was always uncomfortable with it

to him, this would all too easily lead to the aforementioned corruption of that "labour aristocracy" which proclaimed to speak in the name of the proletariat. his solution, at least for russia, was a tight-knit group of highly motivated, committed marxists to retain fidelity

but he soon realized this also didn't work. the "vanguard" was susceptible to corruption too, and there just weren't enough of them (especially after leading cadres got wiped out in the civil war). his last years were spent fighting this (see lewin's "lenin's last struggle")

sartre has an interesting meditation on the problem. he suggests that those committed to class politics can retain fidelity to it by adopting certain epistemological strategies, like always aligning themselves with the most marginalized, both nationally and globally

and to always be open to critique and engage in self-critique, particularly from those groups rather than the "bourgeoisie" (PDF of that text here https://static1.squarespace.com/static/5aa99fa94cde7adaef899f02/t/5b0339b703ce64928f4ff4e8/1526938045729/sartre_socidoc.com_a-plea-for-intellectuals.pdf). but that just collapses into the aforementioned search for personal fortitude, a purely individual act

again, I have no solutions to this, no one does. but being aware of it as a problem that was recognized very early on and people have been grappling with for over a century now is I think helpful, because at least we know what doesn't work