Styling Sen. Dianne Feinstein as a privileged relic of a California that no longer exists, Democratic state Sen. Kevin de León said he would provide a much-needed new voice in the U.S. Senate for a fast-changing state.

“California has changed dramatically in the past 25 years and has become a much richer and diverse state,” the Los Angeles legislator said Thursday in a 90-minute meeting with The Chronicle’s editorial board. “Values have changed dramatically, and the leadership in Washington doesn’t reflect that.”

De León called for voters to contrast his poverty-stricken upbringing in San Diego as the son of an immigrant single mother with a third-grade education to that of Feinstein, whose father was a San Francisco doctor. De León called her “someone who has lived in a mansion surrounded by walls all her life. It’s an issue of values.”

The four-term incumbent projects “an air of entitlement and monarchy and a sense of ownership” when it comes to her Senate seat, he said. “I learned the value of hard work ... in having nothing, in coming from nothing.”

De León would be a far more liberal senator than Feinstein. He said he would support a range of progressive policies, including a national single-payer health insurance system.

And he said he believed there was an impeachment case to be made against President Trump. Feinstein said last week that the president was “erratic,” but declined to say whether she thought he had committed an impeachable offense.

Trump “makes (former President) Richard Nixon look like a choir boy and Watergate like a car burglary,” de León said.

While admitting he had no special insight into the arguments Democrats like billionaire businessman Tom Steyer have been making for a Trump impeachment, “I would advocate it,” he said.

The president’s business dealings, his campaign’s purported links to Russia, potential conflicts of interests and other concerns that have been raised about Trump make impeachment a real possibility, de León said.

“I’ve seen folks go down for much, much less,” he said, pointing to former state Sen. Roderick Wright of Los Angeles, who was convicted of felony perjury and voting fraud charges in 2014 for having what de León called “an address issue in an area where he’s lived all his life.”

De León also slammed Feinstein for her votes to support wars in Afghanistan and Iraq, saying he would have voted against sending U.S. troops to either country. The long-running conflicts have cost countless lives and trillions of dollars that could have been spent on health care and other needs, he said.

“The vote was very consequential,” de León said. On one of the most important votes on national security, “she made the wrong call.”

In a hint of TV attacks yet to come, he also argued that Feinstein was a longtime foe of immigration and immigrants.

Feinstein “has made a career of attacking immigrants since she ran for office the first time,” de León said, pointing to an ad she ran during her 1994 run for her first full Senate term.

The ad accused her opponent, GOP Rep. Mike Huffington of Santa Barbara, of voting against adding more border guards and stated that “Dianne Feinstein led the fight to stop illegal immigration.” In a voice-over, she said she had worked to secure the border with more guards, better lighting and additional fencing.

Bill Carrick, a longtime consultant for Feinstein, brushed off the accusations.

“Most of what she was talking about was border security,” he said, adding that Feinstein took a political risk when she came out against the anti-immigrant Proposition 187 during the same campaign. “She’s been involved in all the immigration reform efforts.”

The campaign is heating up as the June 5 primary approaches, even as polls show Feinstein with a large lead. A Progressive California, a super PAC backed by the California Nurses Association, released a 60-second TV spot Thursday supporting de León. It is now scheduled for a one-day run in Southern California.

The ad blasts Feinstein for her suggestion that Democrats “have to have some patience” with Trump and uses chunks of de León’s February speech at the state Democratic convention, where he told the crowd that “in your state Senate, Democrats act like Democrats.”

But being a Democrat in a Congress controlled by Republicans is very different from leading a state Senate so Democratic that GOP members can be safely ignored.

“I’ve negotiated with Republicans on a variety of big, big issues,” de León said. “I’m not saying I won’t work together with the president or anyone of his advisers” on issues important to the state.”

Trump does make it harder, he admitted.

“Had some other (Republican) ... won the presidency, as a Democrat, as a partisan, I’d be disappointed, but I’d get over it in a week and then look for common ground.”

But he criticized Feinstein for her unsuccessful efforts to work with Trump.

“I’m not foolish enough to think you can secure deals with Donald Trump,” de León said. “I would never let myself be used as a prop,” suggesting that was what Feinstein was when she joined the president at the White House for roundtable discussions on immigration and gun control.

While de León was quick to criticize Feinstein’s policy positions and political decisions, he emphasized that he was not running against the veteran senator or the state’s political — and heavily pro-Feinstein — establishment.

“We need a leader of the moment,” he said. “I’m not running against somebody, I’m running to lead.”

John Wildermuth is a San Francisco Chronicle staff writer. Email: jwildermuth@sfchronicle.com Twitter: @jfwildermuth