The resignation of state Sen. Michael Rubio, D-Shafter, comes on top of other recent vacancies, but Democrats were already expecting to face difficulties in some of their goals later in the year, such as cementing a controversial $150 fee on rural residents whose homes are at risk from wildfires.

Republicans, meanwhile, were expected to have a difficult time capitalizing on the vacancies in Democratic-leaning districts.

Rubio's resignation temporarily drops Democrats to 26 seats in the 40-member state Senate, one shy of a supermajority. That's because two Democratic-leaning seats are currently vacant.

Senate Democrats started the new two-year session with a 27-vote supermajority -- instead of 29 -- because Gloria Negrete McLeod of Chino and Juan Vargas of San Diego resigned their seats after being elected to Congress.

The outcome of special elections to fill their seats this spring could lead to vacancies in the 80-member Assembly, as Democrats in that house run in the Democratic-leaning Senate districts.

Because Rubio is stepping down in the middle of his term, his 16th Senate District -- which includes Kings County and parts of Fresno, Kern and Tulare counties -- will hold a special election under the previous map, said Allan Hoffenblum, publisher of the California Target book, which analyzes legislative and congressional races.

Democrats currently hold 50 percent registration compared to 28 percent for Republicans in that district.

Even though the new district still strongly favors Democrats, Hoffenblum said it will be interesting to see if Republicans put up a fight.

"Republicans are so much talking about what they have to do to elect more Latinos, this might be a good opportunity to recruit a strong Latino and put a good race there," he said.

Assuming Democrats retain all open seats, there will be 29 Democrats and 11 Republicans in the Senate. Democrats hold 55 of the 80 Assembly seats, one more than needed for a supermajority, while there are 25 Republicans.

Meanwhile, Rubio said in an interview that he consulted his attorney and he will not be lobbying. Neither he nor Chevron would disclose his salary with the San Ramon-based company.

"In this role, he will have responsibility for advancing the company's interests in California state politics and public policy, supervising a team of legislative and regulatory analysts and advocates in Sacramento," Chevron spokesman Morgan Crinklaw said in a statement.

State campaign finance records show Chevron gave the maximum contribution of $3,900 in each of the last two election cycles to Rubio's Senate campaign, for a total contribution of $7,800. Chevron donates to most lawmakers.

Rubio was making a base salary of $90,525 as a member of the Legislature along with daily expense payments that can add up to about $30,000 a year. California lawmakers do not receive pensions.

Rubio said his family will remain in Sacramento so his youngest child, who has Down syndrome, can receive care at the University of California, Davis MIND Institute, a research center that works on neurodevelopmental disorders.