They ALSO are eligible for a pension plan after 5 years - it was the latter I was referring to though you are correct that they use Social Security.

Here is the information on their pension plan:

https://www.wwltv.com/article/news/verify/government-verify/congress-members-can-receive-pension-retirement-checks-fact-check/536-fcd98c29-78ed-47ff-8c50-52437cdb4022

I'd read about this years ago.