What does this mean?

“Championed the cause” usually means that you helped lead a movement. Like, “Martin Luther King championed the cause for equality between races.”

And Jacksonian democracy.

The Jacksonian democracy refers to the policies and causes of Andrew Jackson. In this case, his support for extending political power to all men including agricultural workers and industrial workers—rather than keeping it in the hands of the landed gentry (wealthy property owners).

@Marina: And bankers. Oh, did Jackson ever despise those speculators.

Good addition, indicatebound!