Joe Biden’s selection of Senator Kamala Harris was received well across the Democratic Party’s political spectrum, setting up the final push to oust President Donald Trump and take back the Senate from majority leader Mitch McConnell. It also clarifies the challenge that progressives will face after the election.

Pundits celebrated the elevation of a woman of color and a child of immigrants, saluting Biden for repaying the African American women so critical to his victory in the primaries. Climate activists were enthusiastic given Harris’s early endorsement of the Green New Deal and work against environmental racism.

Progressive leaders ritualistically signaled their approval. Jesse Jackson celebrated her as a “proven vote getter,” despite a surprisingly lackluster run for the presidency. Elizabeth Warren hailed her for “when she took on Wall Street during the financial crisis as Attorney General [of California],” a claim that would amuse Treasury Secretary Steve Mnuchin, the “foreclosure king,” whom she refused to prosecute despite evidence of “widespread misconduct.” Bernie Sanders tweeted his congratulations, noting that she “understands what it takes to…fight for health care for all,” despite her awkward retreat from support of Medicare for All, which was costly to her presidential bid. Numerous talking heads suggested she’d turn out a massive black vote, despite the fact that she ran consistently behind Bernie Sanders among black voters. Trump’s insults have helped consolidate her support since she was announced, as he libeled her as an “extraordinarily nasty,” “madwoman,” and his campaign incoherently ranted that she was a too-tough prosecutor who would defund the police, and a socialist extremist too moderate to satisfy the Sanders voters.

In fact, Biden’s choice wasn’t much of a surprise. In addition to repaying those who brought him to the dance, he chose someone who, like himself, is known less for her ideological commitment or her policy acumen than as an establishment politician, responsive to the party’s deep-pocket interests, who tacks to the party’s prevailing winds.

That reality frames the challenge that progressives will face not only in the fall campaign but in relation to a Biden-Harris administration. If victorious, Biden, as he has recognized, will take office amid catastrophic conditions not seen since Roosevelt took office amid the Great Depression. In response, Biden—with a boost from Bernie Sanders—has begun to put forth an agenda embracing bolder measures, from a green growth investment plan to tuition-free college for 80 percent of Americans and more. But the “Roosevelt moment” has far more compelling implications for progressive movements and activists.

When Roosevelt was first elected, he too wasn’t known for his ideological commitment or his policy acumen. Walter Lippmann dismissed him as “a pleasant man who, without any important qualifications for the office, would very much like to be President.” FDR did understand that the economic crisis required bold action. An early flurry of activity—much driven in the “first hundred days”—helped staunch the economic decline but wasn’t sufficient to end the Depression.

What FDR is most remembered for came in what is called the “second New Deal,” the reforms in 1935–36 that included the Wagner Act, which transformed labor law and empowered workers; the Works Progress Administration, which launched massive public works projects; and the Social Security Act, which provided the beginnings of a modern welfare state—including retirement security, aid to dependent children, unemployment insurance, and aid to the blind.

Three elements were critical to these fundamental reforms. The crisis demanded reform and weakened the ability of the discredited business lobby to block it. Mobilized insurgent popular pressure—the growth of militant and increasingly disruptive strikes, the surging popularity of populist movements that challenged FDR politically—pushed Roosevelt and the Democrats to act before the 1936 reelection campaign. Progressive liberals inside and outside the Congress and the administration devised, championed, and drove the reforms—often in the face of Roosevelt’s hesitations.

If elected, Biden and Harris will call for immediate action to address the calamities they inherit. An administration significantly staffed by veterans drawn from the Clinton and Obama years will inevitably be too cautious at home and most likely too expansive abroad. Entrenched financial interests from Wall Street to Silicon Valley will resist fundamental change. If real reforms are to occur, progressives will have to drive them.

Fundamental change will require independent, militant popular mobilization building even in the face of Democratic demands for unity. The historic Black Lives Matter demonstrations, the women’s uprising, the growth of wildcat strikes led by the teacher’s strikes and the Fight for $15, the climate movement, the progressive revival sparked by the Sanders’s campaigns provide kindling for what must grow into a bonfire. As in the New Deal, the weakness of organized labor will require independent organization to mobilize the anger of working and poor people.

As they did with Roosevelt, progressives inside and outside of Congress will need to act independently to craft reform legislation, convene hearings that expose the powerful, and provide public platforms that can drive bolder reforms.

In this regard, the continuing victories of progressive insurgents—represented by the victories of Jamaal Bowman, Cori Bush, Mondaire Jones, Ritchie Torres, and Marie Newman; the sweeping wins of the members of “the squad”(Representatives Alexandria Ocasio Cortez, Rashida Tlaib, and Ilhan Omar) over corporate-funded challengers; and the growth and increasing clout of the Congressional Progressive Caucus under the leadership of Mark Pocan and Pramila Jayapal—put progressive reformers in position to drive the agenda in the Democratic House. Progressive Senators led by Bernie Sanders and Elizabeth Warren plus Sherrod Brown, Jeff Merkley, and a dozen more will have an outsize influence if Democrats take the Senate. On the outside, the proliferation of more sophisticated and progressive think tanks, grassroots movements, and social media networks offers ideas and resources increasingly competitive with the established party network.

An era of reform requires a crushing repudiation of Trump and Republicans in the Senate. Presidential leadership is important. But far more essential are people’s movements and progressive leaders forceful enough to generate gale-force winds of change. That isn’t the responsibility of Biden or Harris. It is the challenge that activists and aroused citizens must meet.