By James R. Riffel

Chargers officials said Tuesday they expect their proposed ballot measure to build a $1.8 billion downtown San Diego stadium and convention center annex will require a two-thirds vote to pass, despite a recent court ruling.

Chargers stadium consultant Fred Maas made the comment during a briefing to several reporters on the initiative, which could be unveiled to the public any day now.

Tax increases in California have required two-thirds public votes, but the state Fourth District Court of Appeal ruled earlier this month that hikes resulting from initiatives need only a simple majority for approval. The ruling is likely to be appealed, making prospects for the Chargers project murky in the November general election.

“We’re operating like it’s two-thirds,” Maas said. “Obviously, the ruling has thrown a curve ball at everybody.”

Maas said the issue will need to be sorted out by the City Attorney’s Office.

According to the presentation by the Chargers, the 65,000-seat stadium and convention center annex would be owned by the city of San Diego under a new joint powers authority.

The Chargers would be responsible for the stadium side of the facility during game days, along with football-related operations and maintenance. They would also agree to a lease of at least 30 years.

The authority would mange the 385,000 square feet of convention center space and the stadium when its not being used for the team.

The stadium side could be used for football bowl games, concerts and overflow exhibit space from the convention center on non-game days, according to the Chargers.    Schematics of how the facility would look are due within a month.

The Chargers said their plan includes chipping in $350 million of their own money and using a $300 million loan from the NFL.

Public funding would come from raising the city’s 10.5 percent hotel room tax to 16.5 percent, which would be among the highest in the nation. The city, however, adds a 2 percent fee to the room tax to pay for tourism promotion, so the effective increase would be just four percentage points.

The resulting increased revenue would pay debt service for bonds on a $600 million convention center annex, $200 million in land and relocation costs, and $350 million in what the team called “integration costs.”

Some of the revenue would be used to maintain tourism promotion and, unless the economy tanks, some money would end up in the city’s general fund, which pays for basic services like public safety and libraries.

The proposed ballot measure does not address future expansion of the current convention center building — which area tourism leaders want in order to keep exhibit floor space together — or the future of the Qualcomm Stadium property in Mission Valley.

The Chargers have been wanting to replace Qualcomm Stadium for around 15 years and have threatened to move to Los Angeles. NFL owners rejected their proposal to build a stadium in Carson, but gave them an opportunity to join the Rams in a future Inglewood facility.

Chargers Chairman Dean Spanos negotiated a placeholder deal with Rams owner Stan Kroenke and then said he would give staying in San Diego — the team’s home for 55 years — another try. The Chargers announced last month they would seek to build a stadium downtown.

Mayor Kevin Faulconer and county Supervisor Ron Roberts had offered a plan to build a replacement on the Qualcomm Stadium site.

The mayor’s office withheld comment until the team’s proposed initiative was released publicly.

James R. Riffel is a City News Service reporter.

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