The third time was not the charm for backers of a Lake County sales tax measure aimed at raising $24 million over 10 years to combat algae blooms in Clear Lake and protect it from invasive mussels.

And there won’t likely be a fourth time, said Scott Knickmeyer, chairman of the Save the Lake Committee, which raised about $50,000 for the Measure S campaign.

“I think we’ll go back to the drawing board to see if there’s another way to get those funds,” he said.

Measure S, placed on the ballot by the Board of Supervisors, had a 63 percent “yes” vote against 37 percent “no” with nearly all precincts reporting Wednesday morning. The tax needed a two-thirds vote, or 66.7 percent, to prevail.

“It’s tough to get that extra point,” Knickmeyer said earlier in the evening, when the measure was falling about 1.5 points short.

The results looked to be “about where we left off with Measure L,” he said, referring to a nearly identical proposition on the June primary ballot, which fell short by 220 votes with 65.2 percent voter approval

A similar measure also failed in November 2012 with 63 percent support.

“I would tend to think we won’t try again,” said Knickmeyer, head of the Lake County Association of Realtors.

Realtors groups contributed about $148,000 to the Measure L campaign earlier this year, and about $21,000 to the Measure S campaign, he said.

Clear Lake, a popular recreation and bass fishing spot, is also an economic cornerstone that “affects pretty much everything in Lake County,” including property values, Knickmeyer said.

The proposed tax measure would have included funding for the county’s share of a $48 million federal project to restore the 1,400-acre Middle Creek area at the north end of Clear Lake, reducing the inflow of nutrients that promote the growth of noxious blue-green algae.

It would also have supported measures to protect the lake from an invasion of quagga mussels that have wreaked havoc in waterways across the nation and made their way into Southern California lakes and reservoirs.

County Supervisor Jeff Smith, who was headed for re-election Tuesday night, said he was still hoping to find a way to improve the lake’s future.

“It will make such a big difference for Lake County,” said Smith, who lives on the lake.