Editor's note: Julian Zelizer is a professor of history and public affairs at Princeton University. He is the author of "Jimmy Carter" (Times Books) and author of the forthcoming book "Governing America" (Princeton University Press).
Princeton, New Jersey (CNN) -- Occupy Wall Street finds itself at a crossroads.
After New York City officials cleared out Zuccotti Park, where protesters had set up a makeshift city, and prohibited protesters from coming back with basic necessities such as tents, activists have been trying to figure out what to do next. A movement that has thrived on the outrage about the power of Wall Street in American life is now spending more time thinking about itself.
Thus far, most of the discussion has been about how to reignite and reorganize the grassroots. But the movement must start to think much more about politics of a different sort.
This step is always difficult from a movement, like Occupy Wall Street, that revolves around a blistering critique of how politics works. There is always the fear that by engaging the political system, a movement will sell out its principles and replicate the experience of their opponents.
But some of the most effective grassroots movements have had a lasting effect because they made the decision to take "formal" politics seriously.
This was certainly the case with the New Left in the 1960s. During the "Age of Aquarius," left-wing activists who participated in the civil rights movement and the anti-war movement were very committed to the principles of participatory democracy. Like Occupy Wall Street and the tea party movement, they too believed that the political system was broken and beyond repair.
In their minds, the Democrats were as bad as the Republicans and were a party that had compromised so much with the status quo that their rhetoric about social justice and the middle class was bankrupt.
According to the founding document of the Students for a Democratic Society, "The American political system is not the democratic model of which its glorifiers speak. In actuality it frustrates democracy by confusing the individual citizen, paralyzing policy discussion, and consolidating the irresponsible power of military and business interests."
The New Left believed that Democrats had embarked on an unnecessary and devastating war in Vietnam, while they only put Band-Aids on problems such as race and poverty.
But by the early 1970s, the New Left weakened as a movement. Government crackdowns on protesters had their toll. The end of the draft in 1973 diminished some of the concerns that had driven middle-class youth to protest, as did the end of America's involvement in Vietnam.
But the New Left did not fade away. Many turned to the world of electoral politics. In the 1972 presidential campaign, people such as future president Bill Clinton devoted themselves to the campaigns of South Dakota Sen. George McGovern, who unsuccessfully challenged President Richard Nixon, and to other candidates who were more successful. Many of the activists would run for Congress or local office.
There was also a massive proliferation of Washington-based interest groups that focused on issues such as civil rights and the environment. These organizations lobbied Congress, raised campaign funds and created ongoing pressure on elected officials. They also pushed for government reforms, such as sunshine laws, to open up the system.
The result was that even as America entered the Age of Reagan, the influence of 1960s liberalism remained alive and well. A new generation of politicians elected to Congress and to local office in the aftermath of the 1960s was profoundly influenced by the arguments about race, welfare and military intervention.
Within a much shorter time span, the tea party has followed a similar path. Although the movement started with the same fiery critique about how politics worked and a commitment to avoid becoming part of the status quo, tea party Republicans have managed to entrench themselves in Washington.
The movement allied itself with sophisticated Washington-based organizations such as Freedom Works. These groups had the organizational savvy and financial muscle to help the movement gain attention from the media and politicians, as well as to organize events. With figures such as former House Majority Leader Dick Armey working with them, the tea party formed a connection to the world of Washington that would have otherwise been difficult.
By the 2010 midterm campaigns, the tea party also focused its energy on electoral politics, playing a significant role in promoting candidates and defining issues that shaped the debate.
Although some of the candidates failed to win election and cost Republicans seats, many succeeded and have put immense pressure on the Republican leadership. The tea party also honed in on the issue of the deficit, in relentless fashion, and pushed the GOP to make certain that it didn't compromise. It is likely that the tea party, even after the activists lose interest, will live on as a result.
The shift from grassroots politics to electoral and interest groups politics is essential for long-term success. At some point, the grassroots energy will fade or government officials will stifle it. As Occupy Wall Street has discovered, protests can also turn ugly and produce a political backlash.
As the weather gets cold, the movement needs to start thinking of what will come next. The first step will be finding candidates who can run for Congress and local office. Van Jones, environmental activist and former member of the Obama administration, has recently talked of plans for 2,000 candidates to seek public office to represent the 99%.
"You haven't seen anything yet," he told CNN. This will be an essential step to translating the outrage into electoral power. Of course, it will require activists to engage in the sometimes unglamorous work of canvassing, recruiting, organizing, knocking on doors and fundraising.
Beyond that, the movement must establish some kind of organizational presence in Washington.
Despite all the talk of the goals of Occupy Wall Street being vague, in the end it has raised a very concrete pair of issues: rising inequality in America and the excessive power of private money in American politics. Both are issues with particular policy solutions, such as ending President George W. Bush's tax cuts that disproportionately benefit the well-off and pushing for campaign finance reform that includes public funds for candidates.
Unless Occupy Wall Street miraculously achieves the kinds of radical transformations some talk about, the occupiers will likely close shop and go home. The alternative is to hold their noses and dive into the kinds of political battles that offer them the best hope to reshape the Democratic Party -- and American policy.
The opinions expressed in this commentary are solely those of Julian Zelizer.