We have seen a revitalization of citizenship in our country this past year. In beating back the repeal of Obamacare, rallying around DREAMers, and through other civic actions, the progressive grassroots community has risen to defend American values and to protect the advancements we made under President Barack Obama. Millions of Americans, many of whom never imagined themselves as political activists, have used their voices to make a difference.

That activism has translated into electoral results. Victories across Virginia, New Jersey, and special elections coast to coast have given Democrats a boost heading into crucial state and congressional elections next year. But, even in victory,  we can’t grow complacent.

It is tempting to assume that our recent successes, if replicated in national elections, will by themselves restore fairness to our system of representative democracy. In fact they show the opposite: Without structural reforms, even a landslide rejection of the governing party won’t necessarily drive its officials out of power in Congress and state governments around the country.

Consider what just happened in Virginia. In races for the House of Delegates, Republicans won only 44 percent of the vote, but have a chance to retain the majority of seats pending a recall. That is a direct result of Republican gerrymandering during the last round of redistricting.

And it’s not just Virginia—Republicans have used gerrymandering to rig maps in their favor in states all over the country. That means if Democrats want to take back the House of Representatives and regain control of state houses next year, they will need to win a wave election of historic proportions.

That is why, with the support of President Obama,  I am serving as the chairman of the National Democratic Redistricting Committee (NDRC). We are the strategic hub for establishing a comprehensive redistricting plan. Following the Census in 2020, states will again redraw congressional and state legislative maps, and we are already hard at work making sure we don’t spend another decade with Republican drawn maps.

We are filing lawsuits in states where maps have been drawn unconstitutionally. We are supporting candidates, like Governor-elect Ralph Northam, who will have critical seats at the table during the next round of redistricting. We will support ballot initiatives for redistricting reform in states where that is a viable option.

And, through our new partnership with Organizing for Action (OFA), we are building a movement to ensure that Americans have their voices heard and are engaged around the issue of redistricting.

OFA volunteers and supporters will help build grassroots infrastructure to engage in this fight. But it won’t be easy and there’s no time to waste.

On Monday, I will be joining OFA volunteers who will be taking their first action on this issue by hosting house parties across the country. Together, we will engage in citizen-to-citizen dialogue to start educating, organizing, and mobilizing support to win these pivotal battles, and bend our democracy toward fairness.

Redistricting can be complicated. The process is different in each state. And progressives begin at a significant disadvantage.

Following the Census and elections in 2010, Republicans took total control of 25 state legislatures and 29 governorships, giving them enormous power over the redistricting process. They used that power effectively, but solely for partisan benefit. A recent report from Princeton noted that “thanks to technology and political polarization, the effects of partisan gerrymandering since 2012 have been more pronounced than at any point in the previous 50 years.”

Recent elections results back this up.

In 2012, Republican candidates for the Wisconsin State Assembly won less than half of all votes but received 60 of the Assembly’s 99 seats.

According to a recent study, in 2016, Republicans won as many as 22 additional U.S. House seats based on how their congressional districts were drawn.

Egregious gerrymandering is quite simply an attack on our democracy. It undercuts the tenet of one person, one vote, which causes people to feel as if their voices are not being heard and to thus disengage from the political process.

Districts that are drawn to protect partisan interests mean that politicians are more concerned about defeating primary opponents than representing all general-election voters. That means on issues like creating access to affordable health care, reducing gun violence, addressing climate change, or reforming the criminal justice system, Republicans have become more willing to cater to the fringe of their party than to find common ground with Democrats.

Next year, 38 governors and 322 state senators will be elected to four-year terms. These elected officials will determine whether, after the 2020 Census, our legislative maps will allow for democratic accountability, or whether the damage being done to our democracy will continue.

We need all hands on deck for a fight we can—and must—win. We need all of you. I hope you’ll join us.

Eric H. Holder, Jr. is the 82nd Attorney General of the United States and Chairman of the National Democratic Redistricting Committee.

Correction: An earlier version of this article stated that 288 state senators will be elected to four-year terms next year. The correct number is 322.