"I swore an oath to protect and defend the Constitution of the United States, not the politics of my party," Moulton, a former Marine Corps officer, told ABC News' "The Investigation" podcast. "And Mueller has made it very clear that we have a constitutional duty to pursue impeachment."
Discussion among House Democrats of whether to open an impeachment inquiry against the president has splintered the party in recent weeks. House Speaker Nancy Pelosi has come out publicly against impeachment, and at the moment its future looks dim given that it lacks support from the majority of the 553 house members. But according to ABC News' count, at least 86 members of the House are in favor of launching impeachment inquiries against Trump.
Moulton said Monday that Democrats should act swiftly to begin impeachment inquiries. He called it a "mistake" not to move forward, and blamed stalls in the process on "people in our party that are afraid to pursue this."
"We spend too much time in this party debating the politics of impeachment when the law is very clear and our constitutional duty is clear," Moulton said. "This is a debate we need to have because it's simply the right thing to do."
Moulton is a 2020 Democratic primary contender, though he failed to qualify for the first presidential debates, falling below both the 1% polling threshold and 65,000 individual campaign donor threshold, one of which was necessary to qualify. He has also so far failed to qualify for the upcoming July 30 debate.
But in his time serving on Capitol Hill, Moulton was and continues to be an early advocate of impeachment proceedings for Trump, and while his previous pushes haven't gained momentum among his colleagues, Moulton told ABC News he feels that now, more than ever, the political tides are shifting in favor of his position.
"I have colleagues on Capitol Hill who are changing their minds, but they're moving in my direction, not away from it," Moulton said.
Moulton said he believes that Mueller's report clearly demonstrates possible obstruction of justice allegations against the president, and reaches the "unmistakable conclusion" that Russian officials worked to elect Trump. Moulton classified Mueller's findings of Russian involvement in the 2016 election as a "national security issue."
Trump has repeatedly denied allegations of obstruction, frequently telling reporters there has been "no obstruction."
Mueller is scheduled to appear publicly for testimony before two House committees on July 24. He has previously publicly stated that his report "is his testimony" and that he would not provide any additional information about his report in a public forum.
But Moulton said the testimony will be a good opportunity for more people to learn about the contents of the report.
"Too few Americans have read it," Moulton said. "I don't think most of my colleagues have even read it."