It's a weird case. Because governing is to a degree a skill. And it takes some time to get OK at it. But when you're around long enough, certain rots set in.
I understand the appeal of term limits, but then you just had veteran staffers and lobbyists who get more ability to direct lost lawmakers (to a degree, it would be like only letting you employ engineers under 32. I assume that would be kinda a mess)
I don't disagree, but my guess is that
for ethical new members of Congress, they steer clear of influential lobbyists at first. And then, over time, after being inundated by them for years, pick the one(s) they deem as least awful and succumb to those.
But it's just a guess. It's probably both/all of the above.
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As for term limits, I think it's essential, but not short ones. Make it 20 years or something...but these guys who hold their seat for 40+ years are garbage. They "rep" stodgy districts with no growth and lazy voters. It should not be a career...maybe a Congressional mentor program to get newbies up to speed more quickly could be a thing - but it'd be a private career to do that.
Anyway, there's far too much of the representative telling their district what they should want and not enough of the district telling the representative to actually BE a representative. Honestly, they should change the name of the job, because I don't see much actual representation at all.