Texas and California — the two most populous U.S. states — are the leading actors in a back-and-forth push to remake the balance of power in the U.S. House, kicked off when President Donald Trump called for Texas to redraw district lines with the GOP’s fragile House majority imperiled in the upcoming 2026 midterm elections.

Texas has been the epicenter of Trump’s push to gerrymander congressional maps to shore up Republicans’ narrow House majority before next year. But the standoff is threatening to into other states — including California.

As a Texas senator summoned the F.B.I. to round up Democrats, the redistricting war that began in Texas was spreading, with California aiming at five Republican House seats.