Bernie Sanders’ campaign to be the Democratic Party’s nominee in the 2016 US presidential election presents the far left in the United States with some hard questions.

For those convinced that the electoral process is a vehicle through which the capitalist class enlists the rest of us in consenting to our own subjection, Sanders’ campaign makes us ask why this time might be different. For those focused on internationalism, anti-imperialism, anti-racism and worker control of the means of production, there seems no principled reason to support Sanders. And for those convinced that only a politics that develops outside the system can change the system, it’s unclear how the campaign is anything but another iteration of the society of the spectacle: enthusiasm is mobilized and directed until redirected onto the next new thing.

But these aren’t the hard questions.

The hard questions involve how, exactly, the left conceives of political change and what we are willing to do to bring it about. The hard questions involve the relations between principle and practice. The more we uphold left principles, the less likely we are to have the capacity to implement them. Our principles become barriers to their own realization. Conversely, the more we get our hands dirty by engaging in the processes that might bring about significant political change, the less left and less significant these changes are likely to be. We will have had to compromise, water down, rank and involve ourselves with strange bedfellows. The dilemma of left politics is that we appear stuck between beautiful souls and dirty hands.

Politics involves knots of principle, compromise, tactics and opportunity. Their push and pull against one another accounts for much of what many dislike about politics: banal rhetoric, betrayals, splits. Finding a candidate or party with which one fully agrees is impossible. Something is always missing, always off.

This is not (only) the fault of the political system. It’s (also) a manifestation of the ways people are internally split, with conflicting, irreconcilable political commitments and desires. After the tragic capitulation of Syriza to the coercion of the European institutions last summer, for example, a taxi driver in Athens explained with a shrug of his shoulders, “What could they do? We wanted two things and couldn’t have both: eliminating our debt and staying with the euro.” Politics forces us to confront conflicting goals: guns or butter, security or freedom, now or later. The conflicts are within us, between us, and between us and the settings in which we seek to intervene.

The institutions through and in which we might intervene are also split. They are not uniform or self-identical. There is disagreement between members and flanks, between candidates and platform, between aspirations and actions. No institution is a uniform whole. It’s always divided, the site of myriad conflicts and struggles always threatening to tear it apart.

A question for left politics, indeed any politics, is the terrain on which to fight. We have to be in the fight if we want to affect its outcome. For many of us, the terrain of political struggle is the streets and the squares, the insistent push of protest. Emphasizing the power of political movements, we push to demonstrate the power of the people, to confront those who seek to control, imprison, and coerce us with the force of our number.

In the US, the most recent examples of such movements are Black Lives Matter and Occupy Wall Street. Not only did both refuse the status quo but both have changed the conditions of political possibility. Because of the advances of these movements, inequality and incarceration, and the racist capitalist structures that intertwine them, are driving the mainstream political conversation in ways that we haven’t seen in a generation.

How do we extend the force of the movements? How do we make them endure? One way is to occupy institutions that have the capacity to realize movement aims. Party and state institutions can be tools and terrains that we seize in order to push our ends. The party isn’t opposed to the movement. It’s a terrain that the movement can occupy.

With regard to Occupy, we all knew that no one could speak for the movement. We all knew that the movement could not be reduced to one group of people in one park. The power of the movement was its capacity to replicate and extend itself, to be more than any city or practice.

The Sanders campaign extends the fight to the terrain of the Democratic Party. Since Bill Clinton’s co-creation and occupation of the Democratic Leadership Council in the 1980s, the Democratic Party has shifted ever rightward, jettisoning any commitment to the working class it might once have had, courting the finance sector and other elements of the corporate elite, and adorning itself with just enough cultural politics to placate its base. No wonder most of the left left the party. Like the other institutions of extreme capitalism, the Democratic Party is not for us. But we can treat it as a site of struggle. Black Lives Matter activists have recognized this crucial fact.

The Sanders campaign is forcing a split in the Democratic Party. Sanders is confronting the Democrats’ claim to democracy with the party’s practice as an instrument of oligarchic political control. He is doing this with the language of social democracy, reintroducing socialism into a political setting based on its disavowal.

The political question this poses for the left is whether we want to join the battle tearing apart the Democratic Party. Instead of treating the party as some kind of authority with the power to co-opt our message, we need to treat it like any street or park and occupy it. The more we engage, the more damage we can do, at every turn demonstrating the gap between people and practice.

If we win, that is, if Sanders gets the nomination, we have access to a political apparatus that extends throughout the US, into every state and community. If we lose, we have gained valuable political experience and created an opportunity for building a new political organization for and of the left.

Just as Occupy was never about one group, so the Sanders campaign is not about him. It’s about changing the conditions of political possibility. The Democrats are terrified of this, which is why they dismantled the rules barring PAC donations to the party.

The left has been alienated from the Democrats yet now their elite is terrified that the left will take it over. We should give them reason to be afraid. When we occupy the party, we continue the movement, pushing the power of the people.

Can “socialism” be part of the mainstream political vocabulary in the US? Can it displace the hegemonic sense of “no new taxes”, “there is no alternative”, and “the era of big government is over”? Is it a term we can fight over and through in the context of a national politics, or is it relegated to the sectarian struggle over twentieth-century failures?

The only way we can be adequate to our principles is if we are willing to fight for them. This means taking on the battles that present themselves. Too often left voices invoke self-organization, as if what this means were clear, as if somehow workers all over the country were but one step away from generating of their own autonomous collectives. This, for example, is the position Ben Reynolds takes in his recent essay on the Sanders campaign for ROAR. But when we join, build and co-opt parties are we not self-organizing? Too often left voices invoke social movements as independent of political organization, as if the momentary presence of crowds in the street translated automatically into power that endures. Such an invocation leaves out the institutions through which movement power becomes political change, the sites where the meaning of the movement is fought over and advanced.

If our goal is to change the world, we should try changing a party as a trial run. If it doesn’t work this time, then we create a new one.