Candidates onstage during the first night of the second Democratic presidential debate on Tuesday night made no mention of either former special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE’s report or impeachment.

The 10 candidates onstage in Detroit were asked questions on a variety of issues such as health care, race, immigration, climate change and the economy, but they did not mention Mueller or the possible impeachment of President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE over roughly 2 ½ hours of debate, nor were they asked about either topic. There also was no talk of foreign interference in U.S. elections.

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Mueller appeared on Capitol Hill last Wednesday to testify before the House Judiciary and Intelligence committees about his 22-month investigation into Russia's election interference.

Mueller didn’t reveal much new information but confirmed key passages from his report, including the fact that he did not exonerate Trump on allegations of obstruction of justice.

A number of House Democrats have come out in favor of opening an impeachment inquiry into Trump since last week, citing Mueller’s testimony.

The House Judiciary Committee on Friday went to court to petition for the release of grand jury material underlying Mueller’s report, with Chairman Jerrold Nadler Jerrold (Jerry) Lewis NadlerDemocrats shoot down talk of expanding Supreme Court Schumer: 'Nothing is off the table' if GOP moves forward with Ginsburg replacement Top Democrats call for DOJ watchdog to probe Barr over possible 2020 election influence MORE (D-N.Y.) saying it was necessary to decide whether to recommend articles of impeachment against Trump to the full House.

House Speaker Nancy Pelosi Nancy PelosiPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline Trump signs largely symbolic pre-existing conditions order amid lawsuit MORE (D-Calif.), however, has remained against opening a formal impeachment inquiry, saying instead Democrats need to see their investigations into Trump and his administration and related court fights play out.

Mueller’s report documents a systematic effort by Russia to meddle in the 2016 election in favor of Trump over his Democratic opponent, Hillary Clinton Hillary Diane Rodham ClintonFox News poll: Biden ahead of Trump in Nevada, Pennsylvania and Ohio Trump, Biden court Black business owners in final election sprint The power of incumbency: How Trump is using the Oval Office to win reelection MORE.

The special counsel did not find sufficient evidence to charge members of the Trump campaign with conspiring with Russia to interfere in the election, though his report documents numerous contacts between campaign associates and Russia-linked figures and states that the campaign welcomed WikiLeaks’s releases of hacked Democratic emails.

Mueller’s report also lays out 10 episodes of potential obstruction of justice by Trump, including the president’s efforts to have his former White House counsel remove Mueller.

The special counsel did not ultimately reach a conclusion one way or another on obstruction of justice, saying the Justice Department Office of Legal Counsel opinion that a sitting president can’t be indicted precluded him from doing so. His report also pointedly states that the investigation does not “exonerate” Trump.

Democrats argue the report puts forth clear evidence of obstruction and that any other American would have been charged if he or she engaged in the same conduct as Trump. Attorney General William Barr Bill BarrHillicon Valley: Subpoenas for Facebook, Google and Twitter on the cards | Wray rebuffs mail-in voting conspiracies | Reps. raise mass surveillance concerns Bipartisan representatives demand answers on expired surveillance programs YouTube to battle mail-in voting misinformation with info panel on videos MORE and then-Deputy Attorney General Rod Rosenstein Rod RosensteinDOJ kept investigators from completing probe of Trump ties to Russia: report Five takeaways from final Senate Intel Russia report FBI officials hid copies of Russia probe documents fearing Trump interference: book MORE, meanwhile, judged the evidence to be insufficient to accuse Trump of criminal wrongdoing.

Trump has attacked Mueller's investigation as a "witch hunt" and claimed the report and the former special counsel's testimony vindicated him after two years of investigation.

Mueller’s investigation received plenty of media coverage over more than two years, and his long-awaited testimony on Capitol Hill last week was carried live on air by major networks. But Tuesday’s debate is an early sign that neither the investigation nor its results will be a major issue during the 2020 campaign.

Mueller’s investigation was also only fleetingly mentioned during the first set of debates last month, before Mueller’s Capitol Hill testimony.