SACRAMENTO  (AP) — The state’s largest union said Tuesday that it has filed a second ballot initiative seeking to boost California’s minimum wage to $15 an hour, setting up a ballot rivalry between two factions of the powerful Service Employees International Union.

SEIU’s state council announced an initiative Tuesday that would raise the minimum wage to $15 an hour by 2020 and require at least six paid sick days a year, double the number now offered to low-wage workers.

Meanwhile, SEIU’s United Healthcare Workers West already has been gathering signatures for a separate measure that would raise the minimum wage by $1 an hour until it hits $15 an hour in 2021. The group, which is backed by Lt. Gov. Gavin Newsom, said it has already collected the 366,000 signatures needed to qualify it.

SEIU hopes both measures can eventually merge to avoid voter confusion and present a unified campaign, said Kristin Lynch, a spokeswoman for SEIU Local 1021, a backer of the newest proposal.

“We are doing our own thing because we think this initiative is significantly different to make that distinction,” she said, adding that the effort is led by the fast food workers who began the effort to raise wages for low-paid workers nationally.

Unlike the already-filed measure, she said SEIU’s state council is prepared to spend $20 million to $30 million for a robust statewide campaign.

The proposals are the latest in a nationwide effort by unions and other groups to raise the wage. The cities of Los Angeles, Seattle, San Francisco, Oakland and Berkeley have approved phased-in increases to eventually take their minimum wage to $15 an hour.

California’s current $9 hourly wage is set to increase to $10 next year. A proposal by Sen. Mark Leno, D-San Francisco, failed to advance in the Legislature this year.

A lower requirement for the number of signatures needed to qualify ballot measures in November 2016 means next year’s ballot is likely to be crowded. As of Tuesday, the secretary of state’s office listed 99 ballot initiatives that are pending or have already qualified.