California is mostly a friendly place for Democrats, but this patch of the state — where the suburban sprawl of Los Angeles comes to an end and the Mojave Desert begins — is still a bastion for the Republican Party and the political territory of second-term GOP Rep. Steve Knight.

The Palmdale Republican won reelection by 6% last fall, but because Hillary Clinton was able to beat Donald Trump by about the same margin in Knight’s district, Democrats consider the seat to have prime pickup potential. The stakes: control of the House in 2018.

Although that election is still more than a year away, Henrickson is part of a group of liberal activists engaged in an urgent battle for voters in places like Santa Clarita. Undeterred by recent Democratic disappointments — four special election losses in GOP districts, including a very expensive one in Georgia — the California activists have taken the long-term view, focusing on districts where incumbent Republicans might be more vulnerable.