SACRAMENTO, Calif. (Reuters) - Democrat Gavin Newsom was sworn in as California’s 40th governor on Monday, and immediately girded for battle with President Donald Trump while flying the banner of his party’s progressive wing.

Newsom took office in a campaign-style inauguration ceremony packed with supporters and media, and featuring nods to California’s multicultural heritage with music from an African-American church choir from the Los Angeles-area city of Compton and a Mexican folk style group dressed in colors of the California flag.

As his 2-year-old son ran on and off the stage, at times pursued by Newsom’s wife, “first-partner” Jennifer Siebel Newsom, the 51-year-old governor vowed to position California - the country’s most populous state with a population of almost 40 million - as a bastion of tolerance and opportunity.

“Make no mistake, there are powerful forces arrayed against us,” Newsom said.

“Not just politicians in Washington – but drug companies that gouge Californians with sky-high prices. A gun lobby willing to sacrifice the lives of our children to line their pockets. Polluters who threaten our coastline and pay-day lenders who target our most vulnerable.”

The Trump administration, he said, is “hostile to California’s values and interests.”

Newsom, a former mayor of San Francisco and former lieutenant governor who led efforts to legalize same-sex marriage and was the political force behind the state’s decision to legalize marijuana, sweeps into office with a three-fourths Democratic majority in the state legislature, dominance that could make the state a bellwether as the national party jockeys to find a candidate to run against Trump in 2020.

Hours into the new job, Newsom signed an executive order that could dramatically reshape the way prescription drugs are paid for and acquired. It directed California’s massive Medicaid system to negotiate prescription drug prices for all its 13 million recipients, changing their benefits from a managed-care or HMO approach to one that allows the state to handle all the purchases.

Ultimately, Newsom wants the program to allow private companies and other government agencies to participate in the negotiations.

RAINY DAY FUND

Newsom credited California’s outgoing governor, Jerry Brown, with righting the state’s finances and leaving it with a well-filled rainy-day fund. But Newsom, who was Brown’s lieutenant governor for two terms, hinted that he would support more spending than the tight-fisted Brown, saying that while the four-term Democrat had built California’s foundation “on a rock,” it was time to build the house above the foundation.

Moves to solve the state’s housing crisis and help more people obtain health care will likely resonate.

“Californians will be looking to Governor Newsom to provide leadership in areas where there are differences in policy between California and Washington, areas like immigration, environment and health,” said Mark Baldassare, president of the Public Policy Institute of California, a nonpartisan polling and analysis think tank.

FILE PHOTO: California Democratic gubernatorial candidate Gavin Newsom speaks after being elected governor of the state during an election night party in Los Angeles, California, U.S. November 6, 2018. REUTERS/Mike Blake

Newsom is expected to seek universal healthcare coverage, push the state to offer free preschool and community college, and continue California’s opposition to Trump’s nationalist stance on immigration.

In 2004, as mayor of San Francisco, he ordered the city-county clerk of San Francisco to issue marriage licenses to same-sex couples, sparking legal battles and cultural change that eventually led to a U.S. Supreme Court decision establishing same-sex marriage throughout the United States.

Although he is socially liberal and economically progressive, Newsom is well-off and not anti-business. A businessman before entering politics, Newsom founded the PlumpJack group of wine shops, cafes and hotels with Getty Oil heir and composer Gordon Getty, a family friend.

His successful ballot initiative to legalize recreational marijuana use in 2016 took into account the needs of businesses and farms seeking to develop a legitimate marketplace for cannabis, while also recognizing that the state government would benefit from taxing it.

The new governor has already staked out some positions in opposition to the Trump administration. Last year, as lieutenant governor and chair of the State Lands Commission, Newsom vowed to block the administration’s proposal to expand offshore drilling in California and other states.

Gun rights advocates are bracing for an onslaught of new regulations under Newsom’s administration, noting that in 2016 he backed a successful ballot initiative tightening gun control laws.