California Gov. Jerry Brown (D), center, walks with Oakland Mayor Libby Schaaf, left, and California State Senate Pro Tem Kevin de León (D-Los Angeles), right, to a Sept. 29 bill signing to help address housing needs in San Francisco. (Eric Risberg/AP)

SACRAMENTO — Holding a pride-of-place spot on State Sen. Kevin de León’s office wall is a painting by a San Francisco artist. The picture renders in water color a roaring bear, the state symbol, its hind legs set in a bed of California poppies.

De León is the Los Angeles Democrat who runs the California state senate, a politician who perhaps more than any other is shaping the character of its political project, which he casts unabashedly in opposition to the administration in Washington. The words that run next to the rampant bear underscore the point.

“California was not part of this nation when its history began,” the script reads. “But we are clearly now the keeper of its future.”

That ambition was declared a day after Donald Trump’s election to the presidency — by de León and Assembly Speaker Anthony Rendon, another Los Angeles-area Democrat. It can be read now as the founding charter of the California resistance, a political ethos that is progressive in spirit, aggressively ambitious in approach, and often expensive for those who live in the state, including those who can least afford it.

The first legislative session since Trump’s election concluded last month and, by all assessments, was one of the most productive in years. Democrats here split the agenda in two: What would have been taken on regardless of who is president, and what was necessary to take on because of who is president.

De León said the session’s goal for the state was to help “make the California dream affordable” in a way that celebrates its cultural diversity and preserves its crackling economy, the sixth largest in the world. But the message beyond the legislative record is as unmistakable as is the man to whom it is directed: Where California heads, so should the nation.

“If John Kasich, Jeb Bush or many other Republicans had won the presidency, I as a Democrat would have been disappointed, but I would have moved on,” he said. “This is uniquely different. Right away we saw that Donald J. Trump was a clear and present danger to our prosperity, to our progressive values and to our people.”

California Senate President Pro Tem Kevin de León (D-Los Angeles) displays a list of various backers of a climate change bill in Sacramento on July 17. (Rich Pedroncelli/AP)

The mythology of California is rooted in a libertarian adventurism that turned out poorly for the doomed Donner Party but has helped enrich Silicon Valley. Now, though, the Western brand of Republican politics once exemplified by Ronald Reagan has been flattened by demographic change and the unpopularity of the party’s national standard-bearer. Trump lost California by nearly 30 points in November and has yet to visit the state as president.

State Democratic leaders are largely unrestrained here by the shrinking opposition. The only brake on their grandest ambitions is their own ideological divide, recognizable as the same fight taking place within the party nationally.

Here the argument has emerged around immigration, regulation and health care — that is, questions about just how expansive and expensive the agenda should be.

Lawmakers passed measures that expanded environmental regulations opposed by Republicans in Washington, declared the entire state a “sanctuary” for its more than 2 million undocumented immigrants and made more transparent the cost of pharmaceutical drug prices at a time when Washington appears unable to move on health care.

“We have shown that we can proceed despite Washington,” said de León, the force behind the California Values Act, the “sanctuary state” law that has been condemned by the Trump administration. “We know Washington is not doing it, so we have to.”

But the costs associated with some of the legislature’s most substantive achievements will fall on California taxpayers in the years ahead, making a state with the highest poverty rate in the country an even more expensive place to live.

Lawmakers increased the gas tax by 66 percent and raised other transportation-related fees. The moves are expected to raise $52 billion during the next decade to rebuild the state’s patchwork roads and creaky bridges — the infrastructure measure, Democrats here say, that the Trump administration has promised and failed to deliver.

To address the state’s highest-in-the-nation housing costs, lawmakers placed a $4 billion bond measure on next year’s ballot and made it easier to build houses within neighborhoods.

“There is a lot of talk about how progressive the session was, but I feel it was very regressive,” said State Sen. Patricia Bates, the chamber’s Republican leader. “Our low- and middle-income folks are going to see the cost of living go way up — and we’re already there.”

Bates represents a stretch of coastal southern Orange and northern San Diego counties that has traditionally favored the GOP’s stand on fiscal issues. She is troubled by the occasional distraction of Trump’s tweeting and, like many other California Republicans, by the implication of some of his statements on race and immigration.

But she is skeptical of the dominant Democratic government in California. She wryly pronounces the opposition’s “resistance” in an exaggerated French accent, and calls much of the agenda “sloganeering and not much else.”

Republicans point to a few measures that will fall hardest on the poor: the 12-cent per gallon increase in the gas tax; higher real estate transaction fees meant to help finance affordable housing construction, and a requirement that a prevailing wage be paid to construction workers for medium-sized and large apartment projects.

That wage stipulation was the price Democrats paid to labor for support the housing package. But Republicans say it will add tens of thousands of dollars to each new project built, making them less affordable.

Bates said Democratic leaders excluded her caucus from much of the legislating this year, except in the move to extend by a decade the state’s cap-and-trade environmental law, which requires greenhouse-gas producing businesses to buy permits to do so.

The bill, a priority of Democratic Gov. Jerry Brown’s, passed with some Republican votes. That support, though, cost the Republican leader in the Assembly his post after the party rebelled, a sign of its division over how much to cooperate with the Democratic agenda.

The Democrats had disagreements of their own.

Brown, who succeeded Reagan as governor in the 1970s and returned to office in 2011, ruled out an early version of the sanctuary state bill because of concerns it raised among state and federal law enforcement officials.

The bill would have prevented state and local police agencies from communication with federal immigration officials and from asking people about their immigration status, among other measures. Brown worried that it would do too much to protect undocumented immigrants who commit crimes.

Negotiations produced a compromise that allows state and local law enforcement agents to work with federal immigration authorities in the jails, leaving the rest of the measure largely intact. Brown signed it into law earlier this month.

The bigger breach came over the push to create a single-payer health insurance program, an enormously expensive undertaking that received support from the powerful California Nurses Association. The measure would have paid the health care expenses of all state residents, including undocumented immigrants.

Cost estimates ran as high as $400 billion a year — more than twice the state budget — and the bill included no way to pay for it. De León pushed it through the State Senate, nonetheless.

But Rendon, the Assembly speaker, would not take it up, to the enormous frustration of the state Democratic Party’s left wing. He called it “woefully incomplete,” positioning himself as a pragmatist to de León’s more aggressive approach.

The idea is not dead, especially with the national health care debate unsettled.

Lawmakers plan to have hearings this fall on the feasibility of a single-payer system, though little is likely to happen before the 2018 election, which will bring in a new governor and senate leader. De León is prevented by term limits from running again; he has announced he is challenging four-term U.S. Sen. Dianne Feinstein (D) in next year’s primary.

“The best resistance is for us is to continue to thrive economically,” said Kevin Liao, Rendon’s press secretary. “Yes, at times, we will fight back, as was the case with the sanctuary state bill. But we were elected as representatives of California and we will continue to take that seriously.”