One-day strikes affected seven Summit hospitals in the San Francisco Bay Area, involving up to 3,200 nurses and several hundred medical technicians.
Prop 32 would ban both unions and corporations from using payroll-deducted funds for political purposes in California.
"You provide the safe neighborhoods, you provide the good schools, you provide the hospitals. We owe you!" Biden declared.
An Embassy Suites hotel was found guilty of denying required paid rest breaks to seven of its workers, and has been ordered to pay each of them about $5,000.
Postal workers and their supporters here were among many thousands throughout the country who demonstrated to save the U.S. Postal Service from austerity measures
The nurses were among 23,000 of their co-workers holding a one-day strike at three-dozen Sutter Health and Kaiser Permanente facilities in northern and central California, as well as Oakland Children's Hospital.
Now awaiting California Gov. Jerry Brown's signature is a bill to greatly strengthen the rights of the state's 400,000 farmworkers.
Bargaining went down to the wire, with the latest session scheduled for today between the United Food and Commercial Workers locals that represent 62,000 Southern California grocery workers and their three grocery chain employers: Ralph's, Albertson's and Vons.
On Tuesday, farm workers launched a 13-day, 200-mile march, through California's rich agricultural Central Valley to the State Capitol in Sacramento.
The civil rights, labor and farm worker community is mourning the loss of Richard E. Chavez, long-time farm worker and civil rights advocate.