On a blisteringly hot Saturday morning in June, 10 days after 30-year-old Katie Hill emerged as the Democratic party's candidate to unseat Republican Steve Knight for California's 25th Congressional district, dozens of her supporters gathered at the campaign's cramped headquarters in the Los Angeles suburb of Santa Clarita to prepare for a massive voter registration drive. This last remaining GOP bastion in Los Angeles County is high up on the list of priorities for Democrats hoping to turn the district from red-to-blue in November.