Sanders actually rose politically thanks to what some would call protest votes. He ran four times in the 1970s for U.S. Senate and governor as a Liberty Union Party candidate, taking 2 percent, then 1 percent, then 4 percent, then 6 percent. He eventually parlayed that into a successful independent bid for mayor of Burlington, Vt., in 1981.
By 1988, Sanders endorsed Jesse Jackson for president when Jackson was running as a Democrat. This, at the time, was seen as a pragmatic move for the socialist mayor. But it came with a catch: He really wanted Jackson to run as a third-partier or independent.
“My own preference would have been, and I would have rather have seen, Jesse Jackson run independently, third-party, outside of the Democratic Party,” Sanders said at the time.
https://www.youtube.com/watch?v=rCv6KMfHIeM&rel=0
— source washingtonpost.com