California Lt. Gov. Gavin Newsom (D) will run for governor in 2018. (Photo by Tony Avelar/Invision for Sonima Foundation/AP Images)

California Lt. Gov. Gavin Newsom (D) on Wednesday told supporters that he will run for the state’s highest office in three years as another piece of the Golden State’s complicated political puzzle fell into place.

“I’ve never been a fan of pretense or procrastination,” Newsom says in the e-mail announcing his campaign for governor. “The reality of running for Governor — even four years from now — in America’s largest, most diverse state demands that I start raising resources now if we’re going to lead a conversation worthy of the 38 million people who live, work, attend school and raise families in the Golden State.”

Newsom, the former mayor of San Francisco, was widely expected to run to replace either Gov. Jerry Brown (D), who is term-limited in 2018, or Sen. Barbara Boxer (D), who is retiring after her term expires in 2016. Newsom bowed out of the Senate race just days after Boxer announced she was out, making a bid for governor all but certain.

The committee Newsom is forming will allow him to raise up to $28,200 per donor per election, or $56,400 for the entire 2018 election cycle. Running for governor is likely to cost $30 million to $50 million, or possibly much more: Meg Whitman, the former eBay chief executive who ran against Brown in 2010, spent $144 million on a losing campaign.

Boxer’s retirement and the term limits Brown faces promised to break a logjam at the very top of California Democratic politics, which have been dominated for years by a trio — along with Sen. Dianne Feinstein (D) — of older elected officials while a younger generation waited for promotions.

Attorney General Kamala Harris (D) jumped into the race for Boxer’s seat just days after the senator said she wouldn’t run. So far, she has cleared the field and racked up a host of endorsements from prominent Democrats in the Bay Area and Los Angeles. She and Newsom, who both hail from San Francisco, were cautious allies, each cognizant of the other’s ambitions and aware that running against each other could provide an opportunity for a rival from Los Angeles.

With Harris and Newsom each lining up in different races, the main rival from Los Angeles with whom they were concerned — former mayor Antonio Villaraigosa — faces renewed pressure to decide his next political move.

Villaraigosa, who left office in 2013, has made his own ambition clear. He has expressed interest in a run for Senate, although he hasn’t made a decision even a month after Boxer said she would retire. And he’s also interested in returning to Sacramento as governor.

Even with his early entry, Newsom isn’t likely to have the Democratic field to himself. State Treasurer John Chiang (D), several members of Congress and Villaraigosa’s successor, Eric Garcetti (D), are all said to be interested in higher office.

The top two vote-getters in California’s primary system advance to a general election, regardless of their party affiliations.