The former lieutenant governor is expected to make the announcement at an 11 a.m. news conference in Santa Maria, his home town.
The announcement will end weeks of speculation about Maldonado's political future. After heavily promoting the re-launch of his campaign last fall, Maldonado has largely faded from public view. It has been nearly two months since he last reported receiving a major contribution.
Maldonado's exit leaves Twin Peaks Assemblyman Tim Donnelly, a more conservative candidate, as the only Republican actively campaigning against Gov. Jerry Brown.
Neel Kashkari, a former U.S. Treasury Department official, is expected to declare his candidacy soon.
No Republican is expected to unseat Brown in this heavily Democratic state, but Maldonado, a moderate, was once considered the likeliest Republican to advance to the November runoff against him.
But Maldonado's campaign was damaged by missteps from the start. Maldonado came under criticism in May when he announced a ballot initiative to repeal California's prison realignment program but highlighted a menacing photograph of an offender who was not released under the program.
Then, after finishing the first half of last year in debt, Maldonado and his original team of advisers split. Maldonado assembled a new group of advisers, including Ron Nehring, the former California Republican Party chairman, and he presented the team at the state party's convention last fall.
Neither Maldonado nor his advisers responded to repeated requests for comment. The candidate said on Twitter late Wednesday, "Jerry Brown is a good Governor; I'd be a better one."
PHOTO: Abel Maldonado speaks to reporters in Sacramento on May 8, 2013. The Sacramento Bee/Hector Amezcua