The Texas Senate on Saturday approved new congressional maps drawn to help Republicans win as many as five more House seats in next year’s midterm elections.

Moves by Texas Republicans and California Democrats to redraw their U.S. House districts could disrupt a rare partisan balance in American politics.

Just as Democratic U.S. Senate candidate Colin Allred was holding a town hall near the Mexican border as part of an “unrig Texas” campaign tour, the state’s Democratic fundraising powerhouse Beto O’Rourke rallied support in Austin for lawmakers who left the state to delay a redistricting plan led by President Donald Trump.