Trump, California Republicans move to block Newsom's redistricting ballot measure

SACRAMENTO, Calif. (KGO) -- As campaigning for Gov. Gavin Newsom's Proposition 50 ramps up, legal challenges are already emerging against his push for a voter-approved redraw of California's congressional districts.

The mid-decade redistricting aims to shore up at least five Democratic U.S. House seats in the midterms - an attempt to offset Texas Republicans' proposed gerrymander designed to keep Congress under GOP control.

On Monday, President Donald Trump threatened to sue California over his redistricting ballot measure.

"I think I'm going to be filing a lawsuit pretty soon, and I think we're going to be very successful," Trump said. "We're going to be filing it through the Department of Justice, that's going to happen."

California Republicans file complaint to remove Prop 50 from ballot

California Republicans are also escalating their opposition. State Sen. Tony Strickland (R-Huntington Beach) said, "I'm going to fight every step of the way," after GOP lawmakers filed a complaint with the California Supreme Court.

"If anybody's rigging the election, it's Gavin Newsom," Strickland said. "What he wants is to make sure that we have no competitive elections in California and have a predetermined election."

The filing asks justices to remove redistricting from the November ballot, arguing Democrats violated the state constitution.

"The legislature cannot break the law and ask for the people later to retroactively give it the power to redistrict," said Mike Columbo, a partner at Dhillon Law Group.

MORE: Gov. Newsom's trolling of Trump attracts attention to complicated redistricting fight

Democrats maintain the proposal is both legal and necessary. Assemblymember Isaac Bryan, D-Culver City differentiated California's process from Texas, in a Tuesday interview with ABC7 News.

"Any time you change the state constitution, the change you are making is currently not in the Constitution. That is why we send it to the voters," he said. "We are asking the voters if this one-time, mid-decade census redistricting can be approved by them as a response to the authoritarian power grab that's happening in Texas."

A spokesperson for California Gov. Gavin Newsom's campaign supporting mid-decade redistricting shrugged off legal threat from Trump and state Republicans.

"Trump's toadies already got destroyed once in court," Hannah Milgrom, a spokesperson for Newsom's "Yes on 50, Election Rigging Response Act" campaign, told ABC News in a statement, referring to the California Supreme Court last week denying a petition from Republican legislators asking for a pause before lawmakers took more action on redistricting.

MORE: CA Democrats avoid disclosing cost of redistricting special election

Loyola Marymount Law professor Justin Levitt says Republicans may face an uphill battle in court, due to SCOCA's decision last week.

"It's extremely unlikely that the California Supreme Court is going to indulge that," Levitt said. "The proposed new map doesn't actually take effect unless and until the voters approve a constitutional change. That is, it's just a piece of paper and designed to be just a piece of paper. Unless the voters approve a constitutional change, it's a thing that has a future trigger, but it doesn't have any legal impact right now."

Levitt added Trump could face similar challenges, citing a 2019 U.S. Supreme Court ruling.

"The Supreme Court said federal courts are going to be out of the business of policing partisan gerrymandering," Levitt said. "The federal courts have retreated from this. Congress didn't act when it could. And now states are in a brawl that's messy for everyone."