Term limits.
no more than 4 for a representative and no more than 2 for a senator.
my idea, based on the fact that i saw term limited politicians continue in government simply by changing office, is to allow a certain number of points (regardless of which offices they hold) before they are forced out of all offices.
say for example, 1 term for a senator is 12 points. 1 term for a representative is 6 points. 1 term for a governor is 10 points. etc. etc..
then let them all have something like 28 or 32 points to spend in public office over their careers. once that is spent, they are done. no more public office of any sort (on a state level or federal level). this would prevent the career politicians that we currently have.