James Lawler Duggan / Reuters

In the conference room Nancy Pelosi once used as Democratic minority leader, she displayed only one item on the walls. She positioned it strategically, just behind and above her seat at the head of a long mahogany table that could accommodate about 30 people. Anyone sitting at the table couldn’t avoid seeing it, and it stared back at them.

It was a portrait of Abraham Lincoln, on the floor of the House, during the single term he served in Congress from 1847 to 1849. Lincoln cradles a book and has a wry look in his eyes.

When House Democrats convened in the room to hash out strategies on policy and politics, Pelosi would point to the portrait and remind them of a Lincoln quote: “Public sentiment is everything.” That instruction guides her today on the matter of impeachment. But it’s easily misunderstood.

For Pelosi, public sentiment doesn’t mean following public opinion, but strategically shaping it so that it’s more receptive to a strategic goal. It’s not just laying the groundwork; it’s fertilizing it. That takes message discipline, unity, and patience—all of which will be necessary as pressure to impeach President Donald Trump continues to build.

Pelosi executed a strategy to shape public sentiment immediately after President George W. Bush’s reelection in 2004, when Republicans expanded their majority by three seats. Bush was pushing for a politically risky overhaul of Social Security. Members of her caucus and outside advocacy groups pressured Pelosi to propose alternative policies. But Pelosi knew that once Democrats offered a solution, they would give Republicans something to attack rather than defend. For nearly two years, Republicans watched their favorability ratings fall, dragged down by a spate of scandals and the unpopular war in Iraq. Only a few months before the midterm election, Pelosi and the House Democratic Caucus rolled out “6 for ’06,” the legislative priorities they would pass if in the majority. Naturally, Republicans took an offensive posture, but by then it was too late. Public sentiment had ripened for a Democratic legislative agenda, the party gained 32 seats in the House, and Pelosi became speaker. Then she mobilized her majority to pass those very priorities. Two years later, in 2008, the electorate rewarded Democrats with an even larger majority. Timing was everything.

On a more mundane level, I caught Pelosi’s ire when I forgot the Lincoln mantra. It was May 2003, only two years into my 16-year tenure representing a fairly competitive district on Long Island, New York. When Republicans offered a new package of tax cuts skewed to the wealthiest, I indicated to the Democratic whip’s office that I was undecided. A few days before the vote, Pelosi hunted me down on the House floor and asked why I couldn’t oppose the measure. When I told her that many of my constituents favored it, she looked me squarely in the eye and said, “Well, educate them.”

Pelosi’s sensitivity to public sentiment requires her to keep tabs on three fronts.

The first is the Democratic caucus. She constantly monitors and measures the mood of her colleagues. She rotates through her office the House Democratic leadership, a wider leadership group called the Steering and Policy Committee, the chairs of various legislative committees, and the leaders and members of dozens of disparate caucuses (the Congressional Black Caucus and the conservative Blue Dogs, the Congressional Hispanic Caucus and the Congressional Asian Pacific American Caucus, the Congressional Progressive Caucus and the moderate New Democratic Caucus). Then she goes to ground, conferring with members one-on-one. Not everyone knows what everyone else is thinking. She and Majority Leader Steny Hoyer do. It’s how they shape consensus.

Pelosi tells her caucus, “Our diversity is our strength; our unity is our power.”

The second is the congressional electorate, which determines which party controls the House. Sure, Pelosi has institutional responsibilities. Yes, she must reflect the progressive values and priorities of the Democratic Party. But she also has a responsibility to keep Democrats in the majority, so that they can fight effectively for those values and priorities. She’s got to win elections.

An impeachment inquiry that results in Trump’s acquittal in the Senate may jeopardize the 31 Democrats in districts where Trump beat Hillary Clinton in 2016. If Democrats lose 18 seats in 2020, they return to the minority just in time for Republicans to try to use gerrymandering to keep them there for a decade. Many Democratic members from those districts tell me that public sentiment, particularly among vitally needed swing voters, is currently against impeachment. Even Republicans recall how the failed impeachment of President Bill Clinton backfired: In 1998, Democrats gained seats in Congress, a rare occurrence for a president’s party in a midterm election.

The third is the presidency. When Barack Obama was president, Pelosi made sure that decisions by House Democrats were calibrated to avoid friction with the White House. Today, Pelosi makes sure that decisions by House Democrats won’t fortify Trump in battleground states including Wisconsin, Pennsylvania, Florida, Michigan, and others. “Trump is goading us to impeach him,” Pelosi recently told an audience in New York. “That’s what he’s doing. Every single day, he’s just, like, taunting, taunting, taunting. Because he knows it would be very divisive in the country, but he doesn’t really care. He just wants to solidify his base.” If Pelosi and Trump agree on anything, it may be this formula: At this moment in time, impeaching Trump minus convicting Trump equals reelecting Trump.

But “this moment in time” does not mean “all moments in time.” Pelosi, remember, believes it’s possible to shape public sentiment. That’s why she’s unleashed her committee chairs to fully exercise their oversight responsibilities by investigating every facet of potentially impeachable offenses: Jerry Nadler of the Judiciary Committee, Adam Schiff on Intel, Maxine Waters on Financial Services, Elijah Cummings on Oversight and Reform. They may find a smoking gun—incontrovertible evidence that crystallizes public support for impeachment and maximizes pressure on House Republican incumbents in moderate districts. Then Pelosi will have achieved her goal: a broader public consensus for impeachment and stronger, if not necessarily overwhelming, bipartisan support.

Progressives worry that if Democrats avoid impeachment with this president, they will set a bad precedent. Just how bad must things get? Fair enough. But for Democrats there’s a worse outcome: a premature impeachment that acquits and helps result in the reelection of Trump with a loyal Republican majority in Congress, an expanded Republican majority in state legislatures, and a permanently hyper-conservative judiciary.

That would fracture and set back the country more than at any time since Lincoln. Which is why that portrait was on that wall.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.