SAN FRANCISCO (KPIX 5) — Former California State Senator and Assemblyman Mark Leno on Monday became the latest politician to join the growing field of candidates running for mayor of San Francisco.

Leno signed the paperwork at City Hall Monday morning. He could possibly become the first openly gay mayor of San Francisco.

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“I intend to shake things up,” said Leno.

Now officially on the ballot for the June special election to replace the late Mayor Ed Lee, Leno said his top priorities will be housing affordability and homelessness.

“We need a mayor to think big and reject cynicism and demand results,” said Leno.

Leno served in the State Senate from 2008 until 2016.  Before that, he was a member the California State Assembly for six years.

He served as San Francisco Supervisor between 1998 and 2002.

His competition so far includes former Supervisor Angela Alioto, acting Mayor London Breed, SF City Attorney Dennis Herrera and Supervisor Jane Kim, who have all declared their candidacy for the race.

Earlier Monday, KPIX 5 learned that California Assemblyman David Chiu has decided not to run for mayor.

In a letter to supporters posted on social media, Chiu said he has decided to continue to focus on pushing through housing legislation in the statehouse and raising his 2-year old son.

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“Many of you have encouraged me to run for Mayor, and I have been humbled by that support. However, after discussions with my wife, friends and allies, I will not be running for Mayor this June,” Chiu said.

“My family comes first,” Chiu continued. “The last 22 months have been a very special (and sleepless) time for Candace and me, and we know we’ll never again experience these precious, formative years with our toddler, Lucas.”

Between now and June, the board can vote to make Breed or someone else the interim mayor to serve until the electon on june 5th.

“I want the board — my colleagues — to do what they think is best,” said Breed. “I’ve had these conversations with members of the board – many are torn on what they want to do, and so it’s really going to be up to my colleagues to make that decision.”

Leno announced he was planning on running for mayor early last year, months before Mayor Lee passed.

Now the election he was planning for 2019 is happening a year and a half early.

He has already raised over $400,000 for his campaign.

“I know, because I’ve been out there for a full year already, that people want fundamental change,” said Leno.

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The deadline for any other candidates who want to run for the office is Tuesday at 5 p.m.