The liberal idea of political change is electing someone who will "work within the system", make erudite arguments to convince the rational and well-intentioned opposition to simply support her plans, and legislate us incrementally in the direction of justice. Then, when she is inevitably replaced by someone else, those changes are reversed--not incrementally, but dramatically. But even without that last part, the general idea is that as citizens we should accept the landscape of our institutions of power and their structural barriers as absolute, and select the person who least offends those institutions to channel them on our behalf. Implied in this calculation is that not only do we have the luxury of time to wait for these changes to eke out across multiple administrations, but in the end we're better off leaving the governance to professionals who know how to navigate the waters of established political norms rather than challenge them. It is for this reason that all liberals are also conservatives, in the broader systemic sense.
The democratic socialist idea of political change is as follows: (1) stake out a clear and uncompromising progressive ideological agenda; (2) unapologetically advance this agenda while publicly naming its main obstacles, both institutional and cultural; (3) galvanize a popular movement to pressure the system from below, so that those who oppose the agenda can expect consequences for doing so; (4) build labor power that can be leveraged against the political establishment until it grants our demands. This is the Sanders strategy, and the answer to everyone naive enough to think "working with Congress" is how structural changes happen in society. Rather than compromise with the atavistic black blob that is the Republican party, Sanders would probably ignore them and go straight to the people, who have always had the power to directly extract concessions from the political establishment but have never been given a president who would side with them.
We don't just have the ability to withhold our mostly pointless vote. We can withhold our most precious and vital resource that the entire system requires in order to function: our labor. That shakes out very differently depending on whether the chief executive is on the side of the rank-and-file or the scabs, the workers or their bosses.
...
In the end, however, even this strategy is not adequate to meet the challenges we are facing. There will still be a powerful, rich, well-connected opposition that will do everything in its considerable sphere of influence to hold back this movement. Throughout the past century or so, that opposition has been none other than the United States government itself, and it has ruthlessly prosecuted its intentions by subverting the governments of weaker states, influencing global commerce in its favor, cynically manipulating geopolitics through sanctions, and generally allowing capital to dictate the limits of our political aspirations (rather than our aspirations dictating the limits of capital). After all, the New Deal passed within living memory; that didn't stop the neoliberal takeover of politics from Thatcher to Reagan to both Bushes, both Clintons, Obama, and now virtually every Democratic presidential candidate. The Civil Rights movement rapidly made strides for women and minorities; Donald Trump is our current president, and we are living through a resurgence of white supremacist fascism the world over. None of these changes will stick as long as the pillars of political action are propped up by exploitation and imperial conquest, and the small minority who reap all its benefits will never willingly cede power to the mass of people.