President Donald Trump’s campaign to tilt the midterm electoral map in his party’s favour has suffered a sharp double defeat in the Deep South. In South Carolina, a coterie of Republican senators broke ranks to reject a redrawn congressional map that would have imperilled the seat of Jim Clyburn, the state’s only Democratic congressman. One dissenting senator declared that “neither my conscience nor my common sense would allow me to stop an election that is already underway”. Simultaneously, a federal court in Alabama blocked a map drawn by the Republican-led legislature, a judicial rebuke that throws the state’s primary timetable into doubt. Coming from within the president’s own party, these actions reveal the limits of his influence over the arcane yet consequential business of redistricting.

Viewed from Washington, however, the Southern setbacks are mere speed bumps in a broader, methodical campaign. Since Trump exhorted Texas Republicans to redraw House districts last year, the party has enacted new maps in Missouri, North Carolina, Ohio, Florida and Tennessee, with Louisiana likely to follow. Republican strategists calculate that the cumulative effect could yield as many as 14 additional seats in November, enough to buttress a fragile House majority. Millions of Americans have already been shifted into new voting districts mid-cycle, often with surgical precision, in an effort to maximise partisan advantage before the autumn contests.

The scramble is unfolding against a wider legal reckoning over how race and partisanship are deployed in the drawing of district lines. The Supreme Court recently curtailed the practice of carving Black voters into extraordinarily shaped “racial districts”, a ruling that supporters argue ends a cynical political game rather than disenfranchising anyone. While that decision tackled racial gerrymandering, it left intact the more pervasive mischief of partisan map-rigging, which has been honed through data analytics to a point where politicians effectively choose their voters. Analysts in London note that the United States remains exceptional among Western democracies for the licence granted to incumbents to design their own electoral terrain.

The resistance in Columbia and the litigation in Montgomery may not prevent Republicans from gaining seats overall, but they signal that even some party loyalists are growing uneasy with extreme boundary manipulation in a hyper-polarised climate. With court cases still unresolved and primary ballots already being cast, the November midterms will test not only the balance of Congress but the resilience of American electoral norms. The chaos of mid-cycle redistricting introduces an element of unpredictability that even a unified Republican majority cannot fully master.