The 2019 mayor’s race began Thursday in San Francisco, as political veteran Mark Leno pulled his papers and became an official candidate to succeed Ed Lee.

“As mayor, I’ll be fighting for renters, homeowners, immigrants and small businesses,” Leno said during a City Hall news conference Thursday morning outside the Department of Elections. Surrounded by about 20 supporters, he promised to tackle homelessness, the scarcity of housing, traffic congestion and the rapidly escalating cost of living.

At age 65, Leno is an elder statesman in San Francisco politics. He was appointed to the Board of Supervisors by Mayor Willie Brown in 1998 and went on to serve a total of 14 years in the Assembly and state Senate. Yet despite his credentials and a number of legislative victories — including state laws to put kill switches on cell phones and raise the minimum wage to $15 by 2022 — Leno is still bracing for what could be a highly contested race.

Many other names are swirling around as possible contenders for the seat, among them Supervisors London Breed, Mark Farrell and Jane Kim, City Attorney Dennis Herrera, and Assemblyman David Chiu. None of them has filed paperwork or officially declared an intent to run, but all have an edge on Leno — they currently hold office.

“They all have a public position to make news and build support, and that sort of thing,” said political consultant Jim Ross. “So if Leno doesn’t start running, he’s going to be in a situation where they’re all building support, and he’s not relevant.”

By starting early, Leno also has the opportunity to soak up campaign money — he said at his news conference that he plans to raise “north of $1 million, if not $2 million” — and to put together a strong political platform for a city suffering multiple economic and cultural divisions. Winning the mayor’s seat means courting votes from homeowners and tenants, techies and service workers, progressives and moderates, and the thousands of new arrivals for whom the name “Mark Leno” won’t have much currency.

“Any candidate seeking the brass ring of the mayor’s office needs a broad appeal to win citywide,” said Alex Tourk, a political consultant and former deputy chief of staff to Lt. Gov. Gavin Newsom when he was mayor.

To run a successful campaign, Leno will have to present thoughtful policy ideas on public safety, clean streets and housing, Tourk said, while tapping into the liberal resistance to the Trump White House.

Leno has solid roots in San Francisco, having arrived 40 years ago to open a small sign company, right after he dropped out of rabbinical school in New York. Over the years, he forged strong connections in City Hall and became a public face of the local LGBTQ community: He and John Laird were the first openly gay men in the Assembly, and Leno was the first openly gay man in the state Senate.

Even so, there’s a long stretch between now and the November 2019 election.

“An election 21/2 years from now is a political eternity,” said Chiu, who would not confirm rumors of his future mayoral bid. “Right now, there’s a ton of work to do in Sacramento in dealing with immigration, health care and the housing crisis, and on fighting the Trump agenda. I’m a thousand times focused on that.”

Political strategist Nicole Derse, who has helped run campaigns for Chiu, said that right now, San Francisco’s politically minded residents should be focused entirely on national issues, such as Thursday’s House vote to gut the Affordable Care Act.

The mayor’s race “is not the right focus for people who care about politics in San Francisco,” Derse said. “It’s not what people should be thinking about.”

But Leno is plowing ahead.

“I could have been coy, or equivocated,” he said Thursday. “But I know I want to do this, and the time is now.”

Rachel Swan is a San Francisco Chronicle staff writer. Email: rswan@sfchronicle.com Twitter: rachelswan