How often do Americans vote in competitive federal elections? In much of the United States, the answer is rarely. That is a strange fact in a nation split almost equally between Democrats and Republicans. The country has ended up here because Americans increasingly live in like-minded communities inside solidly blue or red states — and because House districts are often gerrymandered to guarantee a victory for one party.

Now, at President Trump’s urging, Republicans are moving to take gerrymandering to a new extreme. He has urged his party’s state legislators and governors to redraw congressional districts to maximize the number of Republican seats. In Texas, the Legislature has taken up his call and passed a new map to create five additional Republican-leaning seats to boost the party’s chance of maintaining control of the House in the 2026 midterms. Republicans in Florida, Indiana, Missouri, Ohio and South Carolina are considering similar steps. Democrats in California and elsewhere plan to strike back with their own redistricting, although Democrats probably will not be able to keep pace if the Republican effort expands beyond Texas.

Mr. Trump’s gerrymandering campaign is a cynical attempt to undermine the will of voters. Never before have a significant number of states simultaneously moved to redraw their congressional districts in the middle of a 10-year census cycle, which now seems possible. Their goal is blatant: allow Republicans to retain control of Congress regardless of majority opinion.

This effort is more alarming than many previous gerrymanders, sordid though they were. The typical pattern in modern American politics is for a president’s party to lose control of Congress after his first two years in office, as voters seek to restrain any one politician’s power. Polls suggest that this outcome could happen again next year. Mr. Trump’s approval rating is below 45 percent, and many Americans are unhappy with congressional Republicans for passing a bill that would cut Medicaid to finance tax cuts for the wealthy. In response, Mr. Trump is trying to change the rules so his party can remain in power regardless of what the public wants — and in Texas, Republicans are complying.

Before we lay out the potential solutions, we want to explain how the country has arrived at this point. Extreme gerrymandering was not inevitable. The Supreme Court has the ability to restrict it and long signaled that it might. In 2019, however, the court’s conservative majority changed course and said federal courts could never strike down a state’s map for being too partisan (though courts can still order maps to be redrawn because of racial gerrymandering). By a vote of 5 to 4, in a decision written by Chief Justice John Roberts, the court said that because the Constitution did not provide a measure for determining fairness, federal courts could not come up with their own.

It was a shortsighted, needlessly narrow decision. Over American history, the court has often drawn on the Constitution’s promise of equal protection to safeguard democracy. To take one example, the 1960s decisions that outlawed grossly different-size congressional districts established a standard of “one person, one vote.”