This year, other ballot initiatives are underway or contemplated in Virginia, Oklahoma, Nebraska and Arkansas, all states where Republicans control mapmaking. And anti-gerrymandering forces are pressing a lawsuit in North Carolina’s state court system, aimed at undoing a gerrymandered state legislative map.

But opponents already are working to undo some of those redistricting initiatives. A group tied to the National Republican Redistricting Trust, an arm of the Republican Party, filed a suit last week arguing that a citizen redistricting commission approved by Michigan voters last year is “blatantly unconstitutional.”

In Missouri, a Republican effort to cripple a citizen redistricting initiative that was approved last year passed the State House, though it died in the Senate. Utah Republicans are considering changing a nonbinding redistricting initiative that voters approved last year, just as they already have altered two other unrelated ballot measures. Last week, New Hampshire’s Republican governor, Chris Sununu, vetoed legislation broadly backed by both parties that would have established independent redistricting there.

And in Arizona, where voters approved a nonpartisan redistricting initiative in 2000, Democrats accuse Gov. Doug Ducey, a Republican, of packing political allies onto the panel that vets prospective members of the Independent Redistricting Commission that will draw maps in 2021.

Because the free-speech and election provisions of most state constitutions are stronger than those in the federal Constitution, state-based lawsuits against gerrymandering, like those in Pennsylvania and North Carolina, are at least plausible in most states. But 38 of the 50 state supreme courts are elected, often in highly partisan contests that limit the prospects for those kinds of suits to reach favorable rulings.

A total of 18 states allow residents to place constitutional amendments on the ballot for voter approval, and a number of those states have already moved to nonpartisan mapmaking. In some of the remaining states, the route to getting an anti-gerrymandering measure on the ballot is strewn with technical hurdles.

In the large number of states where ballot initiatives are not allowed, changing legislators’ minds, suing them or voting them out of office are the only ways to rein in partisan maps. And in the wake of the Supreme Court’s decision, legislators have even less incentive to surrender their redistricting power — particularly the power to draw congressional maps — unless legislators elsewhere do the same and create new momentum among voters.