Rep. Rashida Tlaib (D-Mich.) introduced a resolution co-signed by Rep. Al Green (D-Texas) in late March proposing an inquiry into whether Trump has committed impeachable offenses. Tlaib has long been an advocate of impeaching the president—most vocally for not separating himself from his businesses, a possible violation the Constitution’s emoluments clause.

“The president of the United States—after he took the oath of office, after he said he’s going to uphold the United States Constitution—still to this day hasn’t divested in his businesses and has made profits,” Tlaib told MSNBC earlier this week. “I don’t care if you’re a Republican or Democrat. You should be worried about this, because this sets a precedent.”

Mueller’s investigation, while focused on matters outside the emoluments clause, gives the House plenty of fodder for potential proceedings, specifically in regard to obstruction of justice. Since the report’s publication, Reps. Alexandria Ocasio-Cortez (D-N.Y.) and Ilhan Omar (D-Minn.) have voiced support for Tlaib’s resolution. Others, including Sens. Elizabeth Warren (D-Mass.) and Kamala Harris (D-Calif.), have also come out in favor of impeachment—but the House must make the first move.

This is because the U.S. Constitution gives the House of Representatives the “sole Power of Impeachment,” meaning only they can launch the proceedings. The Senate, meanwhile, has the “sole Power to try all Impeachments,” with the Chief Justice of the Supreme Court presiding over the matter.

Only two presidents have ever been impeached—Andrew Johnson in 1868 and Bill Clinton in 1998—but both were acquitted (Richard Nixon resigned in 1974 before impeachment proceedings could get past the House). In all of U.S. history, the House has initiated impeachment proceedings against federal officials more than 60 times, with less than a third leading to full impeachments, and only eight (all against federal judges) actually leading to convictions and removal from office.

In the case of Clinton, the House Judiciary Committee voted to pursue four articles of impeachment surrounding perjury and obstruction of justice. The full House voted to continue with just two of these: alleged perjury in a grand jury testimony and obstruction of justice, both occurring in relation to a sexual harassment lawsuit brought by former Arkansas state employee Paula Jones. The Senate began trial less than a month later in January 1999.

The constitution dictates that two-thirds of the members present must agree on a conviction; Clinton was acquitted by a vote of 55-45 on perjury and 50-50 on obstruction of justice.

In Trump’s case, the Mueller investigation looked into 10 possible instances in which the president could have obstructed of justice. Although the special counsel eventually determined that it could not conclude Trump committed any crime, the report “does not exonerate him.”

Columbia University professor and political author Robert Shapiro noted that while the Clinton case is similar to Trump’s in the amount of “partisan polarization” present, the current situation is of a slightly different caliber.

“It’s one thing to obstruct the investigation of sexual misbehavior. It’s another thing to obstruct justice in the context of Russian involvement in the election,” he told Fortune.

The more than 400-page document says no collusion between Trump’s 2016 campaign and Russian election meddling could be established, but notes that the campaign “expected it would benefit electorally from information stolen and released through Russian efforts.” Moreover, Trump was worried about the effect Mueller’s investigation would have on his presidency and actively tried to stop it, according to the report.

These instances have led even a former Trump transition team member to come out in favor of impeachment, tweeting: “It’s time, it really is.”

“In the face of a Department of Justice policy that prohibited him from indicting a sitting president, Mueller drafted what any reasonable reader would see as a referral to Congress to commence impeachment hearings,” wrote J. W. Verret in The Atlantic.

Whether or not Democrats catch Mueller’s toss is another question.

House Speaker Nancy Pelosi has argued that “the facts regarding holding the president accountable can be gained outside of impeachment hearings.”

“We must show the American people we are proceeding free from passion or prejudice, strictly on the presentation of fact,” she wrote in a letter to her colleagues.

Democratic presidential candidate Sen. Bernie Sanders (I-Vt.) has also spoken out against impeachment. At a recent CNN town hall, Sanders suggested that impeachment proceedings would ignite a media storm to overpower 2020 policy coverage in a way that actually “works to Trump’s advantage.”

Others feel that’s beside the point.

“We can’t focus around political strategy,” Tlaib told MSNBC. “It’s around putting our country first.”

Warren, too, has said lawmakers need to “set aside political considerations and do their constitutional duty.”

The political argument can sway in favor of or against impeachment, said Shapiro. On one had, impeachment proceedings are “a way of keeping trump’s misbehavior very visible” ahead of the 2020 election. This serves both Democratic candidates and Republican primary contenders.

“They don’t necessarily have to impeach,” said Shapiro. “They just have to keep investigating him. That could make the difference in the election.”

The counterargument is that it might mobilize Trump’s base, Shapiro said. Impeachment could also dissuade voters “fed up with the bickering in politics” from turning out at the polls.

In truth, impeachment has a history of backfiring.

Clinton’s approval rating reached an all-time high during his own impeachment proceedings. According to Gallup, Clinton’s average job approval rating in 1998 was 63.8%, or 10 points higher than his overall administration to-date average.

Trump’s average approval rating rests around 43.5%, but a Politico/Morning Consult poll recently found it fell as low as 39% following the Mueller report’s publication—equal to his lowest-ever rating on the poll in August 2017, just after the Charlottesville protests.

Even so, just 34% of voters from this poll believe Congress should begin impeachment proceedings, meaning the majority of the U.S. doesn’t want to see Trump’s future tried in Congress.

“The indication of the lack of public support for the moment tells the Democrats they should not vote to impeach him immediately, but they should try to gather more information and evidence to make a stronger case,” said Shapiro. “The Democrats will know that they have enough evidence to impeach him if public opinion changes, and the evidence plus the change in public opinion is able to convince Republicans in the Senate to vote to convict him.”