Voters here must decide whether employers should have to pay their workers a minimum wage (search) that mirrors the cost of living in one of the nation's most expensive cities.

Proposition L (search), one of 14 measures on the city ballot Tuesday, would impose an $8.50-per-hour minimum wage on all employers in the city, not just those awarded municipal contracts. The state's hourly minimum wage is $6.75, and the minimum required under federal law is $5.15.

The initiative's backers, who include advocates for the poor, labor unions and San Francisco's elected supervisors, maintain that a city-specific pay mandate is long overdue in a place where working parents need to earn about twice the proposed amount to meet basic expenses.

"A full-time worker making $8.50 an hour makes less than $17,000 a year, and people say that seems like a lot. A lot to who?" asked Beth Shulman, the author of "The Betrayal of Work (search)," a book about low-wage workers.

Spearheaded by the city's restaurant industry, opponents argue the measure is ill-timed during an economic recession. They say it is also unnecessary because it would primarily benefit food servers who earn well above the minimum wage when tips are included.

"There is not a cushion to absorb a minimum wage increase, especially a 26 percent increase that is going to some of our most highly paid employees," said Patricia Breslin, president of the Golden Gate Restaurant Association (search).

If it passes as expected, San Francisco would be the first California city and only the third in the nation to set its own minimum wage. Washington, D.C., guarantees its workers $1 more than the federal minimum, which Congress last raised in 1997. Earlier this year in New Mexico, the Santa Fe City Council (search) set a local minimum wage of $8.50 for all businesses with at least 25 employees.

San Francisco's measure is a little more ambitious because it doesn't exempt small businesses from the mandate. The new wage would take effect in three months for for-profit businesses, but would be phased in over two years for nonprofit organizations and firms with fewer than 10 employees.

City contractors already are required to pay their employees an hourly "living wage" of $9 for nonprofits and $10.25 for for-profit companies.