By Ben Christopher, CALMatters
CALmatters is an independent public interest journalism venture covering California state politics and government.
Photo: Sign at San Diego County Registrar of Voters Office in Kearny Mesa directs customers. Photo by Ken Stone
June 23, 2019 (San Diego) - Presidential challengers hoping to glide to victory through California’s newly relevant primary, a heads-up: Your electoral fate may hinge on convincing enough left-leaning millennials to send postcards over the holiday season.