SAN FRANCISCO — California Gov. Jerry Brown is offering intimate gubernatorial dinners to donors who help defeat a targeted November ballot measure, at a time when the governor will be deciding the fate of all new state legislation, the state Democratic Party says.

Proposition 53 would require statewide voter approval on projects that would require more than $2 billion in state revenue bonds to fund. That could complicate the future of two proposed Brown projects, for high-speed rail and for giant twin tunnels to carry Northern California water south.

A fundraising letter by state Democratic Party financial chief Angie Tate on Aug. 9 calls defeating the proposition a priority for Brown and the state party.

“The Governor will be hosting a series of small dinners in August and September to thank those that are able to help on his priorities,” Tate wrote.

The letter also identified an unrelated measure regarding parole as the governor’s other campaign priority.

Sent to lobbyists and other potential donors, the letter raised eyebrows for what some saw as an offer of access for special interests, during a time when Brown has the year’s legislation on his desk for signing or vetoing. The governor has until Sept. 30 to decide on newly passed legislation.

So far, fundraising mainly is pitting Dean Cortopassi, the affluent Stockton farmer and factory-operator who organized the petition drive bringing Proposition 53 to the ballot, against an array of more prominent opponents. Those include the governor, the state Democratic Party, the state Chamber of Commerce, and construction-industry groups.

Opponents say the initiative targets Brown’s proposed $15.7 billion water tunnels in particular, a charge Cortopassi denies.

As of mid-August, Cortopassi and his family had provided all $4.5 million given the measure’s campaign. While both the state Republican Party and the Howard Jarvis Taxpayers Association have endorsed Cortopassi’s initiative, it’s not clear how much they can devote to campaigning for it in a fraught election year.

Asked about campaign plans, Cortopassi says he hopes for grassroots support. Despite Cortopassi’s deep pockets, campaign spokeswoman Marie Brichetto describes his effort as “David vs. Golaith,” given the forces allied against the measure.

On the opposition side, builder trade groups and an organization representing the pharmaceutical industry — which has critical legislation before the governor — have supplied a total of more than $1 million to the No on Prop 53 campaign committee.

No on Prop 53 committee spokesman Steven Maviglio promises a high-profile campaign against the measure. Although Brown has taken a position, he has not publicly campaigned against the measure. And while the governor has a campaign chest of nearly $20 million that he could devote to this or any other political cause, he has not done so to date.

Brown has been notoriously stingy about dipping into his campaign fund, and has not indicated where he plans to spend it.

“It’s an example of what is wrong with the process,” Brichetto said in an email regarding the fund-raising offer of dinner with the governor. “Prop. 53 will give voters a voice and that’s exactly why they are fighting so hard to stop it.”

Asked for comment Thursday on the donor-dinner offer, Dan Newman, a Brown spokesman, said Brown considers each bill on its merits, and no events have been scheduled.