WASHINGTON -- As of Jan. 20, Chuck Schumer will be the most important Democrat in the land. But spend a few minutes with the incoming Senate minority leader and it's clear where the real power lies.

I was interviewing the New York Democrat last week when he paused to take a call. It was about an event scheduled for the next day to highlight a new initiative tallying jobs "outsourced" overseas during the Trump presidency.

Schumer had one question: "Is Bernie coming?"

"He told me he'd come," Schumer continued. "Hold on, I'll call him right now." The party leader had his aides track down Vermont Sen. Bernie Sanders, the populist insurgent who nearly beat Hillary Clinton in the Democratic primaries. "Hey, Bernie, so can you come?" Schumer asked. "We'll do it at a time that's good for you, OK? ... Try to clear it. It's a good event. ... It's right up your alley and you can help us by coming. ... It complements what you're doing. ... We need you."

Schumer hung up. "OK, he'll come."

Sanders didn't come.

But the interruption said much about how Schumer will lead Democrats in the age of Donald Trump. Schumer, though close to Wall Street for much of his career, is wholeheartedly embracing the party's Sanders-Elizabeth Warren populism. This means Schumer, and the Democrats, are ready to fight.

Conventional wisdom says Schumer will be pulled in a moderate and conciliatory posture by the 10 Senate Democrats up for re-election in 2018 in states that Trump won (two of them, West Virginia's Joe Manchin and North Dakota's Heidi Heitkamp, have been wooed by Trump as possible Cabinet secretaries). He'll be pulled the other way by Warren and Sanders, who represent the party's energy.

But Schumer correctly views this as a false choice: The best way to protect endangered incumbents is to let the Warren wing lead.

Schumer's predecessor, outgoing Democratic leader Harry Reid, did his best both in the majority and the minority to protect vulnerable incumbents such as Mary Landrieu and Mark Begich, using parliamentary tactics to avoid tough votes. But a byproduct of this was that Democrats didn't articulate a clear agenda -- and Landrieu and Begich lost anyway.

If Democrats are to have any hope in 2018, they'll need to reclaim the populism Trump stole in 2016. Schumer embraces this. "If you want to appeal to the manufacturing worker in Scranton, the college student in Los Angeles and the single mom making minimum wage in Harlem, one economic message will work," he said. "We just didn't have it" this year.

Schumer pledges to keep his focus almost entirely on the economy. When Republicans hold votes on energy and social issues that divide Democrats, he figures he'll have enough votes to filibuster even if endangered incumbents split off. "We're going to have five, six sharp-edged [policies] that can be described in five words," Schumer said. "That economic message" -- college affordability, infrastructure spending, taxing the rich -- "unites our caucus."

This reflects a broader post-election debate among Democrats. Clinton ally David Brock last week blamed the loss on the party, saying it "faces a crisis of competence at all levels" and calling for a commission to investigate.

Nonsense, reply those in the Warren wing. They say Clinton's economic agenda was a muddled, build-on-success theme when people wanted change. They say Trump got to Democrats' left with working people, and the answer now is to unite behind specific legislation such as expanding Social Security, protecting Medicare from privatization, and raising taxes on the wealthy to pay for infrastructure spending.

If the new president comes Democrats' way, things will get done. If he takes a traditional Republican approach to the economy, Democrats will fight, and Trump's working-class backers will know they were had.

This doesn't mean a Mitch McConnell-style effort to oppose Trump reflexively -- something Schumer told Trump when the president-elect called him recently to discuss infrastructure. "I said to him it's got to be robust, it can't be just tax credits because nothing much will get built ... and it can't cut traditional programs" such as education and Medicare. "He didn't argue with me," Schumer recounted.

Conversely, when Trump contradicts his campaign themes -- a Wall Street banker as treasury secretary, a billionaire private-school devotee as education secretary and a health and human services secretary who wants to privatize Medicare -- he can expect a populist pushback from Democrats.

This, and not incumbent protection, is what will work for Democrats in 2018 and beyond.