In order to secure the nomination, Gore can be made to grant concessions. He's got the right-wing Dems sewed up, but they can't elect him nor guarantee him the nomination. He needs some labor and liberals to be nominated, and all of them to be elected. Candidacies by Wellstone and Gephardt will intensify pressure on him. Of course, these could actually take a nomination and be much better vehicles for left politics.
Unlike Louis, I don't "trust" any politicians, green red, white, or Leninist. None at all. Their behavior stems more from the political environment and economy than from their innards. A 'grass-roots' base or constituencies are not a guarantor either. Politicians of all stripes routinely betray their supporters, if they need to. The trick is make them need not to do it.
The difference to me is the intensity of public opinion, public protest, and the extent of organized political competition from left/third parties. Where I differ from the Apolypticists here is that such a threat need not (and seldom does) threaten the foundations of the system itself. The state is more malleable than that, as Mike E. suggests. Any rational view of history turns up cases and trends of progress with no associated threat of total upheaval. Of course, those help a lot too, when they happen. But you can't suck them out of your thumb.
The second field of action is independent political organization, typfied by the third party movements (Labor Party, New Party, Alliance for Democracy, Green, and others).
A third is popularizing basic, progressive themes through work with advocates, media, etc.
A fourth would be trying to organize Democrats into 'breakaway' groups who would challenge the relevant public officials to get with the program or lose support. This, incidentally, would be my own political preference, but nobody's really up to it.
All of these endeavors stem from a class-based view but, being practical in orientation, are aimed at actually bettering the lot of the working class rather than hallucinating about Kingdom Come.
Cheers,
MBS