Yet out in the country, even in some reliably red states, reform movements have sprouted. South Dakota is one, thanks to three petition drives. One seeks to make primaries nonpartisan and another calls for an independent redistricting commission. A third is for a ballot measure, similar to one in Washington State, that would create a $50 tax credit for each voter to donate to a political candidate; ban campaign contributions exceeding $100 from lobbyists and state contractors; and mandate that independent groups speedily disclose the top five contributors to political ads and electioneering communications made within 60 days of an election.

In April, Nebraska’s Republican-dominated Legislature voted 29-15 to set up an independent redistricting commission. Gov. Pete Ricketts, a Republican, vetoed the bill, but reformist legislators promise a revised proposal in the next session.

Groups like Independentvoting.org, which has grass-roots organizations in 40 states, are mobilizing against the de facto disenfranchisement of independent voters (who now outnumber both Democrats and Republicans) through the gerrymandering of nearly 90 percent of the nation’s congressional districts into one-party monopolies. In states with closed primaries, this denies independents any vote in the primaries, which makes them favorable turf for extremist candidates in the only seriously contested voting.

In addition, nonpartisan local-election primaries, in which all voters can choose any candidate without regard for party, are being pushed by a citizens movement in South Dakota. Louisiana, California and Washington State already use them.

Two dozen states have attacked gerrymandering head-on. Eleven have set up independent redistricting commissions or other politically neutral mechanisms. Legal challenges have been mounted in half a dozen others. In seven more, including Illinois, Indiana, Ohio and Pennsylvania, popular movements, state legislatures and even the Republican governors Larry Hogan of Maryland, John Kasich of Ohio and Mike Pence of Indiana, who is now Donald J. Trump’s running mate, have said it’s time to outlaw gerrymandering.

In April, Governor Kasich won resounding applause from the Ohio Legislature when he called for an end to gerrymandering: “When pure politics is what drives these kinds of decisions, the result is polarization and division. I think we’ve had enough of that.”