The California Supreme Court unanimously ordered Riverside County Sheriff Chad Bianco on Wednesday to immediately halt his probe into potential voter fraud in last November's special election and to preserve all seized ballots.

Bianco, a Republican running for governor, launched the investigation after the Riverside County Election Integrity Team claimed a discrepancy of about 45,896 ballots between those cast and counted in Riverside County for Proposition 50, a statewide measure that passed by more than 3 million votes overall. The proposition amended the state constitution to allow legislature-drawn congressional maps for the 2026 through 2030 elections, a move backed by Gov. Gavin Newsom and Democrats to counter Republican redistricting efforts elsewhere.

Riverside County Registrar of Voters Art Tinoco dismissed the claims, attributing any variance to a misunderstanding of raw data and noting an actual discrepancy of just 103 votes, or 0.016%. Despite this, Bianco obtained search warrants from Superior Court Judge Gail O'Rane, seizing more than 650,000 ballots stored in over 1,000 boxes from the registrar's office in February and March.

California Attorney General Rob Bonta, a Democrat, directed Bianco to stop, arguing the sheriff lacked authority over election materials and that the warrants failed constitutional standards due to insufficient probable cause. Bianco defied the order and seized additional materials. Lower courts issued mixed rulings, prompting Bonta and the UCLA Voting Rights Project to petition the Supreme Court.

The high court's order, issued Wednesday, pauses the investigation pending full review and requires preservation of evidence, potentially including appointment of a special master for oversight. Bonta hailed it as reining in a "rogue sheriff" whose actions created a "constitutional emergency."

Bianco defended the probe as standard law enforcement approved by a judge to verify election integrity and build public confidence. Warrants, unsealed Wednesday at media outlets' request, detailed affidavits from sheriff's investigator Robert Castellanos citing the local group's audit to check for criminal conduct.

The sheriff had temporarily paused the investigation in late March amid legal challenges but resumed after securing warrants. Critics, including elections expert David Becker, called the probable cause thin and rooted in unsubstantiated theories, while supporters viewed it as necessary scrutiny.

Bianco, a vocal critic of state COVID policies and Trump ally, recently lost President Trump's endorsement in the gubernatorial race to rival Steve Hilton. The case underscores tensions over election oversight in a state where Democrats hold supermajorities.