LOS ANGELES (CBSLA) — The race for Los Angeles County sheriff has taken an unprecedented turn, with the results now too close to call after being called overnight for incumbent Sheriff Jim McDonnell.

With 100 percent of precincts reporting, the race had been called for McDonnell overnight. But with the count turning to provisional and mail-in ballots, retired sheriff’s Lt. Alex Villanueva is now leading by 820,333 votes to 815,406 votes, a margin of less than 5,000 votes: 50.15 to 49.85 percent as of Wednesday evening.

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The L.A. County Registrar’s Office said it would release an estimate of the number of provisional and mail-in ballots which remain to be counted Wednesday afternoon.

It has been more than 100 years since anyone has been able to unseat an incumbent L.A. County sheriff. McDonnell has served as sheriff since December of 2014.

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Going into the election, McDonnell had the endorsement of at least four of the five county supervisors who control his budget and had the support of Los Angeles Mayor Eric Garcetti, former Los Angeles Police Chief Charlie Beck, and Los Angeles County District Attorney Jackie Lacey.

Villanueva had the backing of the Los Angeles Democratic Party and the Association of Los Angeles Deputy Sheriffs, the union representing rank-and-file deputies.

Both candidates are veteran law enforcement officers. Villanueva spent three decades with the LASD before retiring earlier this year, while McDonnell was with the Los Angeles Police Department for 29 years — including as second-in-command to then-chief Bill Bratton — before going on to lead the Long Beach Police Department and then being elected sheriff in 2014.

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(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. City News Service contributed to this report.)