SACRAMENTO -- A labor-backed group is running campaign-style radio ads touting Gov. Jerry Brown's plan to build two massive tunnels to deliver water from the Delta to Southern California, even though voters aren't likely to have a say in whether the project gets underway.

Using folksy political satirist Will Durst as its pitchman, the California Alliance for Jobs for the past several weeks has run two minute-long spots in the Bay Area and Sacramento.

"Located near our two largest rivers, 23 million Californians rely on the Delta for their water," Durst says in an ad that ran last week. "It is the heart of our water system. But a rupture in our Delta levies, caused by an earthquake or Pacific storm, could suspend our water supply for up to three years. Our state couldn't withstand such a heart attack."

The ad campaign is notable because of the high-stakes battle being fought out -- mostly out of public view -- between environmentalists and governmental agencies working on the Bay Delta Conservation Plan, the blueprint for the $23 billion tunnel project. The Brown administration is set to release more details of the plan Wednesday at a Milpitas news conference.

Jim Earp, the executive director of the Alliance for Jobs, said he has not spoken with Brown about the ad campaign, noting that his group and Durst have teamed up on pro-infrastructure radio ads for the past 12 years. Typically, the ads run for a week at a cost of $50,000.

The ads, he said, aren't necessarily designed to win votes or even to have voters call their legislators to seek their support. Instead, he said, they are to educate a public that rarely makes the connection between infrastructure needs and the economy.

"It's more linked to negotiations on the Bay Delta Conservation Plan," Earp said. "We are definitely for this project, so we'll advocate for it."

The alliance is made up of contractors, engineers and other trade associations and labor groups that would gain by creating infrastructure jobs.

Jim Evans, a Brown spokesman, said the governor was aware of the ads but his administration had "zero involvement" in them. But, Evans added, "we're pleased to see others educating Californians about the importance of securing the state's water supply to protect our economy."

Brown almost mirrored Durst's words last week when he summed up his water plan to a business group in Sacramento.

"Lots of people depend on the Delta," Brown said. "Fifty percent of Silicon Valley gets their fresh water through the Delta. If those levies should ever fail in an earthquake or because oceans are rising because of climate change or the snow melts too fast and rushes into the Delta, that would cut off 50 percent of the water. East side farmers, west side farmers, Los Angeles: Huge, we're talking a hundred billion dollars in immediate devastation. This is insurance we gotta invest in."

The California Alliance for Jobs' Twitter account retweeted a link to a story containing Brown's quote.

Jack Pitney, a professor of politics at Claremont McKenna College, said it's not uncommon for an elected official and independent groups to have similar rhetorical approaches to an issue. "They draw on the same material, read the same talking points," he said.

The ads help protect a "potentially vulnerable flank" for the governor and helps "build support for something important to both Brown and the alliance," said Dan Schnur, director of the Jesse M. Unruh Institute of Politics at the University of Southern California. "Maybe it quiets down some of the project's critics."

But that's not likely to happen, say the critics, who claim that the ad campaign shows that backers of the tunnel plan are nervous that the costs will go well beyond the projections and that California taxpayers might have to pick up some of the tab.

Under the current Delta plan, water users such as Central Valley corporate farms and Southern California water districts would bear the full cost of the project. A final economic feasibility report, however, has yet to be published.

And there's a "good reason" for that, said Sen. Lois Wolk, D-Davis. "It's incredibly expensive."

Added Wolk: "It sounds like this ad campaign is a run-up to having the Legislature agree to an enormous bond."

It would take a two-thirds vote of the Legislature to change the current bond planned for the 2014 ballot, noted Wolk, who maintained that an ad campaign is a way of "softening up voter attitudes."

Legislators have been talking about cutting down the original bond's size from $11 billion to $6 billion. And Senate President Pro Tem Darrell Steinberg, D-Sacramento, recently suggested that perhaps the water bond could include limits on the volume of water that could run through the tunnels.

But he "did not suggest, propose or float the idea to fund the tunnels through a bond," said Steinberg spokesman Rhys Williams.

Earp, the executive director of the jobs alliance, said a bond has "never been envisioned. This needs to be financed by those who will use the water."

Contact Steven Harmon at 916-441-2101. Follow him at Twitter.com/ssharmon. Read the Political Blotter at IBAbuzz.com/politics.