By MICHAEL R. BLOOD, Associated Press

LOS ANGELES (AP) — Republicans have a lock on power in Congress and the White House. But far across the country in California, the party of Reagan is seeing yet another threat to its fraying relevance.

Democrats who control every statewide office and command the Legislature are pushing changes in two of the state's largest counties that could leave California even more tightly in a Democratic vice.

At issue in Los Angeles and San Diego counties is who draws the boundaries that determine what voters are included in what districts when electing powerful county supervisors — a decision that has broad implications on Election Day.

The moves are being compared to fights over political power in Texas and North Carolina, where court battles are playing out over the legality of election district boundaries that critics say have been drawn to favor Republican candidates.

"Local government is the next big partisan battlefield" in California, said Thad Kousser, a political science professor at the University of California, San Diego. "It's the only place where the Democrats can still gain seats, and it's really the only place the Republican Party is focused on rebuilding its ranks."

Democrats say the changes would recognize diversity and promote transparency in the arcane process known as redistricting. But Republicans fear Democrats are looking to tilt the scales in the non-partisan county races, which could spread in the state that is home to one in eight Americans.

A bill in the Legislature would change the way district boundaries are drawn for the Board of Supervisors in San Diego County, home to more than 3 million people. Republicans now control a majority of the five seats, though Democrats hold a nearly seven-point registration edge in the county.

The bill would scrap a panel of retired judges who now draw the district lines in favor of a commission with 14 members whose political party affiliations would reflect registration in the county. The change presumably would create a panel with a Democratic hue.

"It's basically a power grab," says Alan Clayton, a redistricting consultant and Democrat long involved in efforts to increase Hispanic voting representation.

To the north, Los Angeles County is suing the state to stop a law passed in October that would establish a similar citizens' commission in the nation's most populous county, home to 10 million people.

The lawsuit accuses the state of usurping local control and replacing it with an "unfair and excessively partisan" system that would discriminate against independent voters and violate the California constitution.

The lawsuit predicts that 70 percent of the commission would be Democrats under the law that "will ensure, by design, that commissioners are predominantly members of the Democratic Party."

Currently, a committee makes recommendations on district lines to the Board of Supervisors.

Republicans were widely successful in 2010 elections across the U.S., including statehouse races. They used that muscle in many states to reshape congressional and legislative districts and maximize the clout of conservative voters.

It's been a different story in California, where the GOP has been in decline for years. Nearly three decades have passed since a Republican — — George H.W. Bush — carried the state in a presidential election. Hillary Clinton trounced President Donald Trump in the state by more than 4 million votes.

Democrats have a 3.7 million edge in voter registrations over the GOP, and Republicans could soon be eclipsed in registration numbers by no party at all — independent voters.

San Diego County Supervisor Greg Cox, a Republican, has called the plan to eliminate the panel of retired judges an attempt to establish "blatant political redistricting."

At a meeting last month, he said the retired judges "would be the least likely to have any political bias or represent special political interests."

Democrats say the changes in both counties would reflect a changing California, where Hispanics now outnumber whites.

"If you want the diversity of perspectives necessary to ensure fairness, you are more likely to find that by drawing from a pool of qualified citizens rather than judges," said state Assemblywoman Shirley Weber, a Democrat who introduced the San Diego County bill.