The most important thing for anyone hoping that this isn't a flash in the pan is to begin developing grass roots organizations and activism, and in that way slowly infiltrate the party organizations, much in the same way that the far left infiltrated the Democratic Party, and the socialists and labor unions before them. The leadership will likely support some of these efforts, as they need to retain voter enthusiasm, but it's important to realize that this won't be solved overnight. It takes years to develop such foundations of power, and more crucially, don't ignore state and local politics: those are very opaque corners with a lot of sway in terms of advancing candidates to the national stage.