As Texas Republicans move ahead with redistricting to protect or even expand the GOP’s slim majority in the US House, Democratic-run states, led by California, are pushing forward with their own efforts to draw new maps and add Democratic seats.

Democratic National Committee Chair Ken Martin urged members of his party to forget their usual rulebook and go all in on partisan redistricting Tuesday.

Redistricting is the legal process in which new congressional district boundaries are drawn to take into account changes in population since the last census. Gerrymandering is using the opportunity to redistrict to manipulate boundaries to favor one’s party over the other.