State law requires the Legislature to pass a spending plan annually by June 15 – something that lawmakers habitually ignore. But the key date this year actually may be June 10. That’s when the California Citizens Redistricting Commission will release the first pass on new legislative districts, and Republicans in particular will discover which voters they should worry about most – the conservatives from their own party who are death on taxes or the moderates and Democrats who may be furious if they don’t at least give the people the option of reinstituting taxes that will expire next month. The difference for K-12 schools and community colleges would be a $3 billion increase in Proposition 98 spending if taxes pass or a $1.7 billion cut if they don’t.

Redistricting and the new open primary system, which will take effect next year, are the X Factor in the negotiations between Gov. Jerry Brown and a handful of Republicans. Their votes – two in the Assembly, two in the Senate – are needed for a two-thirds majority to pass a budget that includes about $8 billion in tax extensions. Pension reform, some sort of spending cap on the state budget, perhaps tied to paying down the “wall of debt” that Brown has made a headline, and a relaxation of environmental regulations are said to be the focus of a possible deal with Republicans. But uncertainty over district lines may be the force driving them to the negotiating table.

Legislators like Senators Sam Blakeslee of San Luis Obispo and Bill Emmerson of Hemet in Stanislaus County,*** (see correction below) who were negotiating with Brown in March before the governor ended talks, may be among the Republicans most vulnerable to boundary changes and an open primary. Under an open primary, one election with all candidates will replace primary elections by party; the top two vote-getters, regardless of party affiliation, will square off in the general election. In a potential seismic shift away from conservative Republicans and liberal Democrats, an open primary is expected to yield more power to independent and moderate voters.

Brown hasn’t revealed who he’s talking to, other than to say it’s between four and 10 legislators. The dilemma facing Brown, Senate President pro Tem Darrell Steinberg, and Assembly Speaker John Perez is whether to press for a budget compromise and final vote before or after June 10. Republicans talking with Brown may never have more leverage than they have now to get what they want. While the new legislative maps may frighten more Republicans, they could be different Republicans from the ones talking now. Opening talks with a new cast of Republicans would complicate getting a budget wrapped up by June 15.

Steinberg could be thinking the same thing. He has said he wants to vote on the budget in early June.

Brown on Tuesday told reporters he remains optimistic he’ll get the four Republicans he needs – even though anti-taxer Grover Norquist of Washington, D.C.-based Americans for Tax Reform was at the Capitol jawboning Republicans not to yield on taxes. Giving his Zen reading on Republican body language, Brown told the San Francisco Chronicle, “I read their feelings … as they express them to me. Their words, their affect and their presence speaks volumes. My judgment is we’re getting close to getting the votes.”

*** I clearly have never been to Hemet. As our readers pointed out, it is in Riverside County.