The unexpected death of Mayor Ed Lee has thrown even more intrigue into what was becoming a crowded race to succeed him when his term ended in 2020.

A number of longtime San Francisco politicians were eyeing the desk in City Hall’s Room 200. Board of Supervisors President London Breed is now acting mayor and the board has the option to retain her or vote to choose another candidate to serve until the city’s June 2018 election. The next regularly scheduled mayoral election is in 2019.

Mark Leno, who has served as a supervisor, state senator and assemblyman, had already announced his candidacy for mayor in 2019. He could now run in June, as could Assemblyman David Chiu, who appeared to be positioning himself for a race by attending a string of San Francisco community events during the recent legislative break.

But shrinking a two-year campaign process into six months would be problematic for Chiu, who would have to forgo a possible re-election to the Assembly to run for mayor. He was guarded about his plans on Tuesday.

“There’s plenty of time to talk about the future,” he said. “Today, this week, this month should be about remembering Ed Lee, grieving and celebrating his legacy.”

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In reality, the time frame is tight for all aspiring candidates. The filing deadline for the June 5 election is Jan. 9, according to the city’s municipal election code.

So far, Leno is the only serious player who has submitted official candidate’s papers and started fundraising. His mayoral campaign had raised more than $166,000 by the end of July, and Leno has said the amount will rise to about $400,000 in his next financial statements, which are due this month.

Philanthropist Daniel Lurie has also discussed a possible run. Supervisors Mark Farrell and Jane Kim, who will both be termed out next year, have been talked about as possible candidates. They could face competition from former supervisor and current state Sen. Scott Wiener, who is still outspoken in San Francisco politics and who only weeks ago steered the supervisors’ policy debate on marijuana sales.

Breed was already courting endorsements for a run in 2019 and will probably enter the race in June.

Another potential contender is City Attorney Dennis Herrera, who ran for mayor against Lee in 2011. Herrera’s spokesman, John Coté, said it was inappropriate to comment on his boss’ political future. Farrell, Kim and Wiener also deflected questions about possible mayoral bids.

“Today the focus needs to be on the mayor and his family,” Farrell said.

Kim has said throughout the year that she’s keeping all options open, and some in City Hall speculate that she would seek the city attorney job if Herrera decides to run for mayor.

If the Board of Supervisors were to try to choose an interim mayor, which may or may not be London Breed, it’s unclear whether any candidate would win the required six votes. The moderate and progressive wings of the board seemed more fragmented this year than in the past, creating doubt that either group would coalesce around a single candidate.

Leno, who has endorsements from four supervisors — Aaron Peskin, Sandra Lee Fewer, Norman Yee and Ahsha Safai — seems to have the best shot. He declined to discuss politics on Tuesday, saying he is mourning Lee with everyone else.

More likely, Breed will continue to serve as acting mayor until June, which may give her an advantage. Or it could make her beholden to her board colleagues, who could vote someone else in as mayor any time before June 5.

Jason McDaniel, a political science professor at San Francisco State University, said the acting mayor role really elevates Breed, who is positioning herself to be the first African American woman to hold San Francisco’s top office.

Breed will likely inherit the “Willie Brown-Gavin Newsom-Ed Lee cross-racial coalition that wins citywide elections,” McDaniel said. Chiu might have soaked up some of that coalition vote if he had had the luxury of a two-year campaign.

Breed seemed unflappable Tuesday as she delivered an encomium to Lee on the mayor’s balcony in City Hall, to an audience that packed the foyer and spilled into the second-floor corridor.

From the outset, the acting mayor compared herself to Lee, noting several times that both of them had grown up in public housing.

“We believed in a city where a poor kid from public housing could become mayor,” Breed told the throng of reporters, politicians and city officials. Her speech was as much a coming-out address as it was a memorial.

If she decides to run, Breed would follow a path similar to the one cut by now-U.S. Sen. Dianne Feinstein, who was the Board of Supervisors president in 1978 when Mayor George Moscone and Supervisor Harvey Milk were assassinated by former Supervisor Dan White. Feinstein served the remainder of Moscone’s term and was elected to the post the following year.

Similarly, Lee was named mayor in January 2011 by the Board of Supervisors following former Mayor Newsom’s election as California’s lieutenant governor.

After a campaign by political insiders and the Chinese community, Lee agreed to run for the seat. He was elected in November 2011 and won re-election in 2015. Lee, the longtime city administrator, was a soft-spoken and unexciting bureaucrat, a striking contrast to Newsom, an idea-a-minute politician whom opponents criticized as being more flash than substance.

Any politician who hopes to win a spring election will have to contend with growing dissatisfaction among San Francisco voters. Although Lee was twice elected, in recent months his poll numbers were poor. A recent Public Policy Polling survey reported 50 percent of voters had a negative view of the mayor, driven largely by his seeming lack of ability in aggressively solving problems such as skyrocketing housing prices, traffic congestion and widespread homelessness.

Leno emphasized such quality-of-life issues in his early campaign speeches, saying that it’s time to take San Francisco in a new direction.

But he stopped short of criticizing Lee.

Audrey Cooper is The San Francisco Chronicle’s editor in chief. Rachel Swan is a San Francisco Chronicle staff writer. Email: acooper@sfchronicle.com, rswan@sfchronicle.com Twitter: @audreycooperSF @rachelswan