Former Attorney General Eric Holder Eric Himpton HolderThe Hill's Campaign Report: Trump's rally risk | Biden ramps up legal team | Biden hits Trump over climate policy Biden campaign forming 'special litigation' team ahead of possible voting battle Pompeo, Engel poised for battle in contempt proceedings MORE argued Thursday that 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 on the special counsel investigation into the Trump campaign and Russia's election interference revealed "grounds for impeachment."

In an interview with NBC News, the former Obama administration attorney general said instances of potential obstruction of justice outlined by Mueller's findings rose to the significance of impeachable offenses, while cautioning the House to wait until Mueller testifies to come to a judgement on the matter.

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"Oh, I think there are grounds for impeachment" in the report, Holder said Thursday. "I said, if you look at the second part of the report, there's no question that obstruction of justice does exist in the findings that Bob Mueller reported, and in painstaking detail. And that in and of itself would be the basis for impeachment."

"But I think the House needs to gather evidence, we need to hear from Bob Mueller," Holder continued. "They need to get the entirety of the report, and then make a reasoned decision."

Holder added in the interview that he does not think that America is yet in a "constitutional crisis," as some Democratic members of the House have suggested, but remarked that the White House's response to congressional subpoenas was "forming up" to be considered such a crisis.

"I'm concerned about the state of this nation and the way in which the Trump administration is reacting to the legitimate request from Congress," the former attorney general said. "We could be in a constitutional crisis, but I don’t think we're there quite yet."

House Judiciary Committee Chairman Jerrold Nadler (D-N.Y.) argued earlier in May that the White House had driven the nation into a "constitutional crisis" by blocking Attorney General William Barr Bill BarrHarris faces pivotal moment with Supreme Court battle Hillicon Valley: DOJ proposes tech liability shield reform to Congress | Treasury sanctions individuals, groups tied to Russian malign influence activities | House Republican introduces bill to set standards for self-driving cars McCarthy threatens motion to oust Pelosi if she moves forward with impeachment MORE from releasing an unredacted version of Mueller's report.

"We’ve talked for a long time about approaching a constitutional crisis. We are now in it,” Nadler said at a press conference.

"Now is the time of testing whether we can keep a republic, or whether this republic is destined to change into a different, more tyrannical form of government," he added. "We must resist this."

Dozens of House lawmakers have backed previous efforts to introduce articles of impeachment against the president, but Democratic leadership has so far been adamant about opposing the tactic.