A California legislative hearing turned into a shouting match Tuesday as a Republican lawmaker clashed with Democrats over a partisan plan to rewrite U.S. House maps to win Democrats more seats. A committee voted along party lines to advance a new congressional map in response to a Republican redistricting effort in Texas that President Donald Trump wants.

Republican legislators filed an emergency petition with the California Supreme Court, arguing Democrats are blatantly violating the state Constitution by rushing bills through the Legislature that would create new voting districts.

RCP senior elections analyst Sean Trende, who advised Virginia's post-2020 redistricting, said Democrats may regret redrawing California's maps in response to a controversial move from Texas Republicans. With many blue states already "maximal gerrymanders," Trende explained how the GOP has a lot...