A defined benefit pension is based on longevity. The determination of the pension benefit is based on years of service on the job and pay.
The very concept is contradictory to being an elected official. Congress was never intended to be a career and yet we encourage that by having a retirement system for members of Congress.
To obtain any benefit from the system requires voters to re-elect members of the House at least twice and a Senator at least once. Giving the longevity of many Members, we are pretty good at that.
Rather than encouraging career politics, we should restructure the compensation package to make it more feasible for average Americans to serve and then to return to private life.