The U.S. Census Bureau has released the long-awaited results of the 2020 Census, triggering the nation’s once-a-decade redistricting process. States must now begin to redraw the districts that will elect members of Congress and of the state legislatures, accounting for any changes in population so that all districts’ numbers of residents are roughly equal.

Because Republicans control many more state governments than Democrats, and because many Democratic-led states use bipartisan or independent redistricting commissions, some observers expect Republicans to gain seats in Congress.

Fewer have noted that the GOP’s redistricting advantage could ensure Republican control of dozens of state legislatures for the next decade. In a few state legislatures, Republicans could draw themselves supermajorities, giving them the votes to override a governor’s veto.

The GOP’s gerrymandering of state legislatures

Republicans very effectively gerrymandered congressional districts to their advantage during the last redistricting cycle, leaving little room to gain more seats. Although some Republican-controlled states will be gaining seats and a few Democratic states will be losing a seat in 2022, this is unlikely to increase the Republican advantage: Much of the population growth in red states is occurring in areas that favor Democrats.

As a result, state legislative seats are likely to see the most far-reaching changes.

In our new book, “Gerrymandering the States,” we studied how states redrew 95 state legislative district maps during the 2011 redistricting cycle. To identify partisan gerrymandering, we used actual district-by-district election results to calculate a partisan asymmetry score for each map before and after redistricting. That score measures the degree to which a map gives one party a higher seat-share than it does to the other party for achieving a similar share of the statewide vote.

For instance, if each party won 50 percent of the statewide legislative vote and then had 50 percent of the state legislative seats, the total asymmetry would be zero, indicating no bias. But if each party won 50 percent of the statewide vote and yet Republicans took 75 percent of the legislative seats because of how districts were drawn, the total asymmetry would be 50 percent.

We defined extreme partisan gerrymandering this way: One party would get an average of at least 10 percent more of the seats than the other party would get for the same statewide percentage of the vote. For example, if the Democrats and Republicans split the statewide vote, but Republicans got 55 seats (in a legislature with 100 seats).

We found that, after 2011, 45 state legislative maps had been drawn with extreme partisan gerrymandering. Of these, 43 favor Republicans, while only two help Democrats. Because of these gerrymandered maps, Republicans held onto power after losing the statewide popular vote in Virginia in 2017, and in North Carolina, Pennsylvania, and Wisconsin in 2018.

GOP-run state legislatures could rig the districts even more in their favor

With some effort, GOP-run state legislatures could draw state legislative districts so they’re tilted still more in the Republicans’ favor.

For instance, right now Ohio’s congressional map ensures that Republicans win 12 of the 16 congressional districts when they get between 50 and 60 percent of the vote statewide, which happened in every election from 2012 to 2020. While it’s difficult to imagine Ohio Republicans expanding this advantage even further — particularly since the state will lose a district in 2022 — they could draw even more bias into the state legislative maps.

We’ve given Ohio’s congressional district map an asymmetry score of about 36 percent in favor of the GOP. But the state legislative map gives only Ohio Republicans a 22 percent advantage in the state house and a 27 percent advantage in its state senate.

Or consider South Carolina, where in 2020 Democrats took only one of the seven U.S. House seats despite winning about 43 percent of the statewide vote — a Republican advantage of about 30 percent, by our estimates. The state house and senate plans are drawn with comparatively less bias, favoring Republicans by 19 percent and 15 percent respectively.

It seems unlikely that the state GOP could redistrict the state’s lone congressional Democrat James E. Clyburn out of office. But the Republicans could draw the map to give themselves more than two-thirds of the state legislature’s seats — and therefore the ability to overrule any gubernatorial veto.

What are the stakes in state legislative redistricting?

In many states, the legislature is in charge of redistricting both its own election boundaries and those for Congress. That means the controlling party can protect its majorities and influence the political makeup of Congress for the next decade and beyond.

Because the U.S. Constitution gives the states broad discretion administering elections, state legislative gerrymandering means political parties can enact laws that make it more difficult to vote, thereby suppressing their political opponents.

After 2011 redistricting, we found state legislatures with extreme Republican gerrymandering were more likely to pass voting rights restrictions. Since former president Donald Trump’s “Big Lie” that fraud stole the election from him, Republican legislatures have been working to further restrict voting rights.

What’s more, state legislatures can gerrymander their own maps to give one party veto-proof power. In North Carolina, Republicans need only three seats in the house and two seats in the senate to achieve the 3/5ths majority required to override a governor’s veto. In South Carolina, Republicans majorities in both houses fall just below the two-thirds veto override threshold. Several other Republican-led states may also be just one map away from veto-proof power.

Taking redistricting away from partisan legislatures

So what can be done? As we’ve written here at TMC before, putting district maps in the hands of independent or bipartisan redistricting commissions can prevent partisan gerrymandering. For instance, California’s citizens redistricting commission drew bias-free maps in 2011, our research found.

But passing such reforms can be difficult. California shifted to such its commission after a popular referendum in 2008; so did Colorado, Michigan, and Utah in 2018. Many states do not give voters that power. Although the U.S. House passed legislation that has now gone to the Senate requiring independent redistricting commissions, that would only apply to drawing congressional districts — leaving state legislatures skewed.

In 2018, the Supreme Court ruled the federal courts cannot hear partisan gerrymandering challenges. State courts might be the only option for some citizens fighting unfair district maps.

Alex Keena is an assistant professor of political science at Virginia Commonwealth University.

Michael Latner is a professor of political science at California State Polytechnic University and senior fellow at the Union of Concerned Scientists’ Center for Science and Democracy.

Anthony McGann is professor of government and public policy at the University of Strathclyde.

Charles Anthony Smith is a professor of political science and law and the University of California-Irvine.

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