The situation has all the elements that the president seeks: a showdown with a top political rival in a deep blue state over an issue core to his agenda.It is the fight President Trump had been waiting for, a showdown with a top political rival in a deep blue state over an issue core to his political agenda.In bypassing the authority of Gov. Gavin Newsom of California, a Democrat, to call in the National Guard to quell protests in the Los Angeles area over his administration’s efforts to deport more migrants, Mr. Trump is now pushing the boundaries of presidential...