House Democrats have opened yet another new investigation into President Donald Trump and his administration, this time focusing on whether Trump lied in written testimony provided to Special Counsel Robert Mueller’s team during their investigation into whether Trump’s campaign collaborated with Russian officials to alter the outcome of the 2016 presidential election.

On the same day that President Donald Trump offered to testify, in writing, in the House’s impeachment inquiry, Democrats unveiled their latest probe, telling the D.C. Circuit Court of Appeals through the House’s official counsel, that they are “now investigating whether Trump lied to special counsel Robert Mueller in written answers he provided in the Russia investigation,” per a tweet from journalist Shimon Prokupecz.

The House’s general counsel, Douglas Letter, noted the new investigation in his arguments to the D.C. Circuit Monday, begging the court to allow the House access to information Mueller collected during his two-year long investigation.

Rep. Jamie Raskin (D-MD) appeared to confirm the investigation in an interview with CNN, according to Mediaite, and suggested that the investigation could be retribution for similar investigations conducted during Bill Clinton’s presidency — investigations that ultimately led to Clinton’s impeachment.

“It’s a crime to lie to federal prosecutors in the course of a federal proceeding. That’s perjury. It was also the basis for the GOP-controlled house’s impeachment of Bill Clinton for lying under oath, for committing perjury. So it’s a very serious offense – and it’s obviously something that we take seriously,” Raskin told CNN’s “At This Hour.”

Democrats are likely following up on information revealed during Trump ally Roger Stone’s trial, which provided the public with more background on Mueller’s investigation, and where the team probing Trump campaign supporters’ affiliations with the Russians hit dead ends, according to CNN.

The Mueller Report itself contained much of Trump’s testimony to Mueller’s investigators, including Trump’s answers “to dozens of questions from Mueller’s office relating to key aspects of the investigation into whether the Trump campaign conspired with Russia to interfere in the 2016 election,” USA Today reported at the time. The questions centered around five key topics: ” The June 2016 meeting at Trump Tower with members of Trump’s circle and a Russian attorney, the Kremlin’s hacking efforts, the Trump Tower Moscow project and the various contacts with Russia during the campaign.”

In Stone’s trial, prosecutors tried to drive home the idea that the Trump campaign — and perhaps even the now-President — was more interested in obtaining damaging information on its political opponents than previously thought, and lawyers sought to demonstrate that Mueller was unable to draw conclusions about Stone’s and others’ involvement with both the campaign and the Russians because of missing and deleted information and unwilling witnesses.

Now Democrats seem eager to compare what was discovered in Stone’s trial to what was made available in Mueller’s report, though details about the Democrats’ specific requests are still forthcoming.

Bill Clinton was, of course, impeached for lying under oath about his involvement with White House intern Monica Lewinsky, and Democrats have clearly not forgotten the roadmap to impeachment provided by Clinton-era Republicans.

The investigation into whether President Donald Trump demanded information on Hunter and Joe Biden from Ukrainian officials in return for an open pipeline of U.S. aid, and the subsequent impeachment inquiry, don’t seem to be going as well as Democrats anticipated, perhaps because the sequence of events is hard to understand and the testimony being given is largely from sources that heard about the alleged quid-pro-quo secondhand. Last week, Democrats tried to adjust their messaging, saying in interviews that they were seeking evidence of “bribery,” out of fear that “quid-pro-quo” was a meaningless phrase to most Americans.

Ultimately, perjury would be an easy lift; Democrats could say that they are impeaching the current president for the same “high crimes and misdemeanors” Republicans used in the 1990s.