Barack Obama has backed Gavin Newsom’s plan to redraw California’s voting map. The former US president said it was a necessary step to stave off Donald Trump’s efforts to redistrict Texas, which would favour Republicans in the state.

It all amounts to the opening salvo in what is likely to become a national showdown to grasp power through gerrymandering.

Obama reportedly said the California redistricting plan, which is being proposed in response to a Texas redistricting that could add five GOP seats in the U.S. House, would only be used if Texas Republicans follow through with the new congressional map.