In the national struggle over U.S. House control, perhaps no politician has more at stake than the California governor, who has emerged as the leading Democratic adversary to President Donald Trump in what many see as a lightly masked trial run for his own future White House bid.

The California governor is adopting a combative social-media persona as well as partisan gerrymandering to counter the president.

Gavin Newsom's press office has been mocking President Trump with tweets in his style over the past few weeks.