A few weeks into his first term as mayor of San Francisco in 2004,
Newsom was ultimately vindicated, with gay marriage gaining public acceptance and becoming legal in California and three dozen other states. But at the time, even some of his supporters thought he was committing political suicide.
As Newsom, now lieutenant governor, prepares for a gubernatorial campaign in 2018, he finds himself at a similar crossroads. This time, his issue is the legalization of marijuana for recreational purposes.
Although legalization would probably be popular with liberal and young voters, others Newsom must court in his run for governor could present a challenge.
"He could motivate large numbers of young people who aren't regular voters to turn out for him," said Dan Schnur, director of USC's Jesse M. Unruh Institute of Politics. "But taking a leadership role on this could make older swing voters nervous, even if they agree with him on the issue. It's a potentially risky play."
Voters in California legalized medical marijuana in 1996 but 14 years later voted against recreational use, 53.5% to 46.5%. Since then, polling has shown that public support for legalizing pot has grown, reaching 53% in a March survey by the Public Policy Institute of California — a record high in the organization's surveys.
Democrats, whites, blacks and people ages 18 to 34 showed the greatest support, with more than 6 in 10 favoring legalization. Older Californians were more skeptical. The state's two fastest-growing voter groups, Latinos and Asians, strongly opposed it.
Even among Democratic policymakers, the matter remains controversial: Both U.S. Sen. Dianne Feinstein and Gov.
"How many people can get stoned and still have a great state or a great nation? The world's pretty dangerous, very competitive," Brown said on
Newsom expresses support for legalization in terms of criminal and social justice, saying African American and Latino youths are more likely than others to be criminally penalized for recreational marijuana use. He insists he has never smoked marijuana and hates the smell.
"This is not ... a flippant debate about stoners and potheads. This is serious stuff, and I don't want to be part of the status quo," Newsom said in an interview, brushing off potential political implications.
"I'm happy to take that risk because I think people will be benefited in a profound way if we do this right…. People like me, we come and go, we're a dime a dozen. This is a principle that will transcend [us]."
Newsom's critics say he is seizing on the matter out of political convenience.
"Gavin Newsom has a history of looking for someone else's parade that he can run to the front of, in order to promote himself," said Ron Nehring, a former state Republican Party chairman who unsuccessfully challenged Newsom in his 2014 reelection bid. "Certainly this is the latest example of that."
Nehring argues that there are ways to address concerns about how the criminal justice system treats users without increasing consumption of marijuana, which he laments would be the natural outcome of legalization.
As mayor of San Francisco, Newsom had a history of courting controversy.
He was burned in effigy when his "Care Not Cash" program replaced subsidies for the homeless with housing and support services. He expanded city healthcare for San Francisco residents, regardless of immigration status, preexisting conditions and employment status — the first universal healthcare program in the nation.
However, same-sex marriage — popular locally but toxic for Democrats nationally back then — has best defined his political persona.
When the California Supreme Court in 2008 upheld same-sex marriage, an ebullient Newsom declared at a San Francisco City Hall news conference: "This door's wide open now. It's going to happen, whether you like it or not!"
Newsom's proclamation became the centerpiece of a television ad by proponents of a successful ballot measure later that year to define marriage as between a man and a woman.
Democratic consultant Garry South is among those who thought Newsom's foray into gay marriage was "political death." But as an advisor to Newsom's short-lived gubernatorial run in 2009, he found that voters in focus groups viewed Newsom's move as "an act of conscience" — precisely because there was no political benefit to it.
"There's always a downside to being out front on a controversial or even semi-controversial public policy issue," South said. "But I got to give Newsom credit. He had a certain amount of prescience about the same-sex marriage issue that no one else at the time had."
Newsom is approaching marijuana legalization far more cautiously.
He chairs a commission of law enforcement, medical experts and others that was created by the American Civil Liberties Union of Northern California to study the issue.
The group recently released a report listing dozens of areas of inquiry, including how marijuana should be taxed, how to assess drivers under the influence of the drug, and how the substance could be advertised and sold to consumers without increasing its use by teenagers.
Public input on these topics will be solicited across the state over the next three months.
"I want to see it done right, and that's why I'm telling all these groups I want to be supportive of a ballot initiative, but it has to be the right one," Newsom said.
"We have to be accountable and responsible for making sure that we address the intended and unintended consequences of any effort to legalize, tax and regulate marijuana for adults.
"It's not good enough to put something on the ballot and begin after the fact to ask those questions."
Bruce Cain, a political science professor at Stanford University, said it was wise for Newsom to anticipate fallout from a legalization proposal or its implementation.
"If he's going to be the lead person, the last thing he needs is for this to blow up for him," Cain said.