What would “Armageddon” look like? Well, the likeliest version is the possibility that such changes to a few districts ripple across the map, endangering additional Republican incumbents.

The Republican-controlled state legislature would probably be able to contain the damage if it got to redraw the map itself. The federal court has asked both sides whether they would be available for a remedial hearing in August or September, a sign that the court might redraw the map instead. A court-drawn map might not be nearly as generous to the Republicans as a map drawn by the legislature.

It’s hard to know exactly how the courts, or the state, would choose to adjust surrounding districts. But demonstration plans brought by the plaintiffs and an old, ambitious court-drawn map from 2011 give a sense of what an “Armageddon map” might look like. Michael McCaul’s relatively safe Austin-area district could become competitive. Mr. Hurd’s district could become so Democratic that he would stand no chance of winning re-election.

In the Dallas area, a new minority-majority district — a district where the majority are racial or ethnic minorities — could require shifts that further endanger Pete Sessions, who represents a district that narrowly voted for Hillary Clinton. It’s even possible that the reconfiguration of the south-central Texas districts could nudge the Houston-area districts of John Culberson or Pete Olson in the Democratic direction.

But even a court-drawn map wouldn’t necessarily cost the Republicans six seats; they would just make those six seats notably more vulnerable. A far-ranging 2011 court-drawn map was struck down by the Supreme Court precisely because it did not do a good enough job of deferring to the legislature; that’s why the temporary one was so modest in scope. As a result, even a court-drawn map is likely to preserve the state’s intent to protect Republican incumbents.

There’s just one way for the courts to truly cost the Republicans four or five seats: require even more minority-opportunity districts in Dallas and Houston. The court did not seem especially receptive to this possibility in April, and many of the plaintiffs aren’t even arguing for such an expansive ruling. But there are demonstration plans that still propose those additional minority-majority districts. The most far-reaching plan could easily yield six or seven new Democratic districts in 2017.