Pelosi is watching more than just the national polls that show most of the public doesn’t support impeachment. She is also wary of animating the president’s voter base for the 2020 election and opening a trial that would give the Republican-led Senate the chance to acquit him.

Even while Pelosi urges restraint, she has sharpened her response to questions about impeachment, saying Trump is “obstructing justice,” and “engaged in a cover-up.” She said at a Thursday news conference that Trump, for political reasons, actually wants Democrats to try to impeach him, and she characterized him as frustrated that they are not yet “on the path to impeachment.”

These mixed messages from Pelosi — urging caution and recognizing that impeachment could be “unavoidable” — reflect the delicate job of balancing aggressive congressional oversight with the need to preserve her majority in the House and deny Trump re-election in 2020.

Faced with resistance from the Trump administration to committee probes, some Democrats are increasingly looking to an impeachment inquiry as the legal justification to enforce subpoenas, pushing Pelosi to begin the process despite the political risks.

“Ignoring subpoenas, obstruction of justice — yes, these could be impeachable offenses,” Pelosi said Thursday. “How we deal with it is a decision that our caucus makes, and our caucus is very much saying, whatever we do, we need to be ready when we do it.”

In a series of press statements, public letters and an aborted meeting this week, Pelosi and Trump, two of the most powerful people in the U.S., traded taunts and questioned each other’s sanity. They faulted each other for abandoning bipartisan negotiations on infrastructure and trade. Trump called Pelosi “a mess” and “crazy.” She said she prays for the president and suggested his family or staff should have “an intervention.”

Trump also tweeted a video clip that had been altered to exaggerate stumbles in Pelosi’s speech.

While she has long questioned Trump’s fitness for office, for almost two years Pelosi said Democrats should withhold judgment on impeachment until they saw Special Counsel Robert Mueller’s report on Russian interference in the 2016 election. Yet that report, released in a redacted form last month, failed to give Democrats a clear path forward by neither conclusively clearing Trump of wrongdoing nor providing irrefutable examples of the “high crimes and misdemeanors” the Constitution says would merit removal of a president.

The Mueller report did provide various strings to pull in probes led by Judiciary Chairman Jerrold Nadler and Intelligence Chairman Adam Schiff, who have subpoenaed administration officials like Attorney General William Barr, former White House Counsel Don McGahn and former communications director Hope Hicks. Those efforts join other investigations of Trump’s administration and businesses, led by Financial Services Chairwoman Maxine Waters, Oversight and Reform Chairman Elijah Cummings and Ways and Means Chairman Richard Neal, all of which Pelosi has praised as responsible fact-finding.

Two court decisions helped Pelosi make her case in favor of these investigations, when federal judges swiftly and decisively moved in favor of committee demands for Trump-related financial records.

“Two in one week!” Pelosi told reporters. She said the judges “resoundingly affirmed” the legislative authority to seek Trump-related financial records from Deutsche Bank AG and other financial records from accounting firm Mazars USA LLP.

The Intelligence Committee this week also reached an agreement with the Justice Department to begin turning over some counterintelligence and foreign intelligence materials from the Mueller investigation.

Pelosi often highlights the need to bring public opinion along with whatever action Democrats take. While one Republican, Justin Amash, a Michigan representative who often bucks the party, says Trump has committed impeachable offenses, most GOP politicians and voters continue to defend Trump, with little indication that uncovering more facts would change their minds.

“But facts can be inconvenient things,” Virginia Representative Gerald Connolly, the top Democrat on the House Subcommittee on Government Operations, said in an interview. Though he is himself reluctant to embrace impeachment, Connolly said it “gets harder by the day, because I face facts with this president and this administration that push me to the impeachment process as part of my oversight and constitutional duties.”

The Democrats who are clamoring for impeachment argue that weighing politics in the calculation to not impeach Trump would be an abdication of their constitutional duty. Progressives like Representatives Alexandria Ocasio-Cortez of New York and Rashida Tlaib of Michigan say Trump’s alleged offenses and continued stonewalling provide more than enough reason to begin the process.

Yet they and other progressives are not the ones whose re-election is at risk should Democrats appear to be overreaching. One House Democrat close to Pelosi said the speaker worries that a rushed impeachment resolution would put some of her 40 freshmen at risk in next year’s election. At least 33 of those members — part of the New Democrat Coalition — are mostly business-friendly, pro-trade progressives, many from areas in which Trump has at least some popularity.

They are the ones studying lessons from 1998, when Democrats picked up five seats after Republicans impeached President Bill Clinton.

Some of Pelosi’s closest lieutenants worry that the day will never come that Republicans would convict Trump of anything.

“There’s a valid argument that if you fail to bring an impeachment, what does that say about this president’s conduct and whether he’s fit for office?” Schiff said at a public event Wednesday. But, he added, “that has to be weighed against the other concern, which is, what does an acquittal say? Because then you have an adjudication” that Trump’s conduct is not impeachable.

James Clyburn of South Carolina, the House Democrats’ top vote counter, backs Pelosi’s go-it-slow approach. Still, he acknowledged Thursday that dozens of his colleagues joined calls for impeachment in the weeks after the Mueller report’s release, though he has not taken an official count.

Some Democratic presidential candidates have also called for impeachment.

Echoing Schiff’s concern, Clyburn said it is likely Trump would be acquitted by the Senate.

“So we’re supposed to impeach, which is an indictment. The Senate, two-thirds of the Senate, will never agree to convict,” Clyburn said. The results, he said, would be to “leave Trump waving a non-conviction in front of the voters next year, simply because a political group decided he wasn’t convicted.”

At least one senior Democrat, Jackie Speier of California, suggested that House Democrats should open an impeachment inquiry and avoid the risk of acquittal by not sending any findings over to the Republican-led Senate.

“It’s all about laying it out for the American public,” Speier, a Pelosi ally, said in an interview Wednesday.

Asked if that would amount to a show trial, she said no, suggesting not many people have read the Mueller report and an impeachment inquiry would bring its findings to light.

But using impeachment for advancing investigations and how the public would perceive the process, are two very different things, according to Ross Baker, a political scientist from Rutgers University in New Jersey.

“I understand the value of the impeachment process as a exercise in fact-finding,” says Baker. “But it will also give a boost to Trump’s claims of victimhood and ‘presidential harassment.’”

Despite the pressure to begin impeachment, a House official familiar with Pelosi’s thinking said no one is going to move forward with a process the public doesn’t want. And for now, the official said, Pelosi knows the public simply doesn’t want impeachment.

More must-read stories from Fortune:

—What would impeachment look like in Trump’s America?

—Bernie Sanders has a message for Trump on trade

—Trump keeps alluding to extending his presidency. Does he mean it?

—Meet the Republicans likely to challenge Trump in the 2020 primary

—Is the Muslim Brotherhood a terrorist organization? Trump thinks so