Atlanta Congressman John Lewis voiced support for impeaching President Donald Trump on Tuesday, a watershed moment that’s expected to push House Democratic leaders to reconsider their reluctance on the issue.

The civil rights hero, who’s viewed as a singular figure of moral righteousness within the Democratic caucus, said the American people will never find out the truth about Trump’s actions unless the House launches an impeachment investigation.

“I truly believe the time to begin impeachment proceedings against this president has come,” he said in a stirring speech on the House floor. “To delay or to do otherwise would betray the foundation of our democracy.”

Lewis has long been a vocal critic of Trump's. His comments that he did not see Trump as a "legitimate president prompted the Republican to attack his Atlanta district on Twitter. He's since boycotted Trump's State of the Union addresses and refused to appear with him in public , including at the opening of a civil rights museum in Mississippi.

Despite that, Lewis  remained on the sidelines of the impeachment debate in recent months out of respect to Speaker Nancy Pelosi, his longtime ally who has urged a slower, more methodical approach to investigating Trump.

That changed this week as lawmaker after lawmaker voiced concerns about Trump's recent admission that he pressed Ukrainian President Volodymyr Zelensky to investigate presidential contender and former Vice President Joe Biden and his family. Hours before Lewis' floor speech, his colleague Hank Johnson, D-Lithonia, became the first sitting Georgia congressman to back impeachment.

Lewis said the Trump administration has demonstrated “complete disdain and disregard for ethics, for the law and for the Constitution.”

“They have lied under oath. They've refused to account for their actions and appear before (the) legislative body, which has the constitutional right to inquire about their activities,” he said.

Lewis added: “The people have the right to know whether they can put their faith and trust in the outcome of our elections. They have the right to know whether the cornerstone of our democracy was undermined by people sitting in the White House today. They have a right to know whether a foreign power was asked to intervene in the 2020 election. They have a right to know whether the president is using his office to line his pockets."

Read more: Lewis, Johnson become first Ga. House Democrats to back impeachment