During the interview, Stephanopoulos asked Nadler if he believes Trump has obstructed justice.
A committee of the US House of Representatives is seeking documents alleging obstruction of justice, corruption and abuse of power by President Donald Trump and his aides.
The New York Democrat has repeatedly expressed his view in recent months that Trump either clearly obstructed justice, or attempted doing so, by seeking to curtail special counsel Robert Mueller's investigation into possible Trump campaign collusion with Russian Federation during the 2016 presidential election.
House Judiciary Committee Chairman Jerry Nadler (D-NY) on Sunday said that the Justice Department's current practice of not indicting sitting presidents requires that the department release any evidence of crimes President Donald Trump has committed, even if he is not charged with a crime while in office per the practice.
"It's very clear that the president obstructed justice", he added, noting, however, that it was too soon to consider whether impeachment should be pursued.
The requests would also look at potential abuses of power, the person said, including the possible dangling of pardons and witness tampering, as well as Trump's broader attacks on the entities investigating him and the press.
Congressional investigators will also look at whether Trump used the White House for personal enrichment in violation of the Constitution's emoluments clause, he said.
U.S. President Donald Trump speaks at the Conservative Political Action Conference (CPAC) annual meeting at National Harbor in Oxon Hill, Maryland, U.S., March 2, 2019. We may or may not get there.
"Impeachment is a divisive issue in our country, and let us see what the facts are, what the law is, and what the behaviour is of the President", Pelosi said.
That investigation was subsequently taken over by Special Counsel Robert Mueller, who is expected to deliver his findings to the US attorney general within weeks.
Congressman Douglas Collins of Georgia, the top Republican on the Judiciary Committee, said he and his staff received no advance notice of the document requests, learning the news from Nadler's TV appearance.
"Show me where the president did anything to be impeached.Nadler is setting the framework now that the Democrats are not to believe the Mueller report", he said.
"Before you impeach somebody, you have to persuade the American public that it ought to happen", he finally said. "But this investigation goes far beyond collusion", he said.
Judiciary Committee Democrats will continue building their possible impeachment case Monday, when dozens of demands for documents will be issued to administration officials and the president's business interests. "You have to persuade enough of the - of the opposition party voters, Trump voters, that you're not just trying to..." We may not get there.
In that case, Nadler said, "we will subpoena, we will do whatever we have to do".