Los Angeles County voters have shown they are willing to pay to get the homeless off the streets but do they care enough to shoulder another tax hike?

That will be seen March 7 with Measure H, a ballot initiative that would raise the county’s sales tax by a quarter-cent for 10 years, generating roughly $350 million a year specifically earmarked for homeless services.

The measure, which requires two-thirds approval, is intended as a companion piece to Measure HHH, a $1.2 billion homeless housing bond passed by city of L.A. voters in November with 77 percent support.

Measure H spokesman Thomas Newman said the campaign is employing two nontraditional strategies: using volunteer networks to get the word out and targeting likely voters. As an example, he pointed to an effort by the United Way of Greater Los Angeles to mail postcards touting the measure to 75,000 likely voters.

But will it be enough?

“As the experience with HHH in November shows, homeless funding measures have been quite popular among voters of late,” said Raphael Sonenshein, executive director of the Pat Brown Institute for Public Affairs at Cal State Los Angeles. “But it does have to get that two-thirds margin, and knowing the 15 percent to 20 percent of registered voters who will turn out will be crucial.”

The measure enjoys support from a coalition of business, civic, and nonprofit groups, including the Los Angeles Area Chamber of Commerce; Los Angeles County Business Federation, or BizFed; and the Central City Association.

“The passage of Measure HHH in November 2016 by 77 percent in the city of L.A. was a strong start,” said Gary Toebben, chief executive of the chamber, in an email newsletter. “Now we need the services to go with the housing.”

Those services would include social workers reaching out to the homeless and on-site clinics at shelters and housing facilities to administer financial benefits and treatment referrals.

The aim of both measures is to put a significant dent in the region’s escalating homeless problem. Last year’s count of homeless found nearly 47,000 throughout the county, and homeless encampments have sprung up in nearly all of the county’s 88 cities.

While there is no organized opposition, the measure faces two significant hurdles: getting more than the two-thirds vote margin and resistance to higher sales taxes after a wave of recent hikes that have tax rates in some cities near 10 percent.

That rate is beginning to far outpace Los Angeles County’s neighbors.

Sales taxes in Orange and San Bernardino counties cities near the Los Angeles County border range from 7.75 percent to 8.25 percent. So, if Measure H passes, the sales tax on a $2,000 big-screen television purchased in Long Beach would be 10 percent, or $200, while the sales tax on that same set in neighboring Westminster and Orange County would be 7.75 percent, or $155.

“We would warn people that the sales tax load is becoming extremely heavy in Los Angeles County,” said Kris Vosburgh, executive director of the Howard Jarvis Taxpayers Association, an anti-tax group in Los Angeles that hasn’t taken a formal stance on H. “People should think as to whether or not this will drive more commerce out of the county. It’s going to look like a bargain to do your shopping in one of the surrounding counties.”