SACRAMENTO (AP) — California’s new top-two open primary system is getting its first test in special elections in two Southern California state Senate districts Tuesday, ushering in changes that proponents hope will eventually lead to a less partisan Legislature.

Voters are choosing successors for Democratic Sen. Jenny Oropeza, who died in office last year of complications from a blood clot, and former Sen. George Runner, a Republican who was elected to the state Board of Equalization in November.

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Under the voter-approved primary system, candidates from all recognized political parties are on the same ballot. The top two vote-getters, regardless of party, advance to a runoff election if no one receives more than 50 percent of the vote.

Voters opted for the new system last year as a way to promote less partisan candidates.

“It’s going to put pressure on members of both parties to be responsive to the needs of a larger group of constituents than they used to,” said Republican strategist Kevin Spillane, who is not involved in either race. That’s because candidates who don’t attract support across party lines may not get enough votes to advance.

In the special elections, there will be no runoff if a candidate receives an outright majority.

There will almost certainly be an outright winner Tuesday to succeed Runner in Senate District 17 because there are only two candidates, both from Lancaster: Runner’s wife, former Assemblywoman Sharon Runner, and Democrat Darren Parker, a small-business owner. The district includes parts of Kern, Los Angeles, San Bernardino and Ventura counties.

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Things are more uncertain in the eight-way contest to succeed Oropeza, of Long Beach, who represented Los Angeles County’s 28th Senate District.

Democrats including Gov. Jerry Brown tried to help former Assemblyman Ted Lieu, D-Torrance, win an outright majority in Tuesday’s election to avoid an April 19 runoff.

Brown and Senate President Pro Tem Darrell Steinberg, D-Sacramento, campaigned for Lieu on Friday as they sought support for the governor’s proposal to close the state’s $26.6 billion budget deficit over the next year and a half. Brown has proposed about $12.5 billion in spending cuts and borrowing. He wants lawmakers to ask voters in a June special election to extend temporary income, sales and vehicle tax increases for an additional five years.

“It’s a major pitched battle, and in the Senate we have 24 Democrats. Ted Lieu will be our 25th Democrat, two shy of the magic number to put a two-thirds vote together that will allow the people to decide the future of California,” Steinberg told Lieu’s supporters. Democrats hold a 24-14 lead over Republicans in the Senate with the two seats vacant, but need 27 votes for the two-thirds majority required to pass tax or fee increases.

Lieu faces a fellow Democrat, Kevin McGurk of Venice, along with four Republicans: Jeffrey Fortini of El Segundo, Martha Flores Gibson of Long Beach, James Thompson of Lomita and Bob Valentine of Manhattan Beach. Only Lieu and Valentine have spent significant money on the race, according to filings with the secretary of state.

Two candidates are running with no party preference: Michael Chamness of Venice and Mark Lipman of Los Angeles.

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