"Investigating these threats to the rule of law in an obligation of Congress and a core function of the House Judiciary Committee", he added.
In their letter, the Democratic leaders allege that Trump, on multiple occasions, "appears to have taken steps to hide the details of his communications with President Putin from other administration officials, Congress and the American people", noting that Trump reportedly "seized notes" related to at least one meeting held with Putin and "directed" an American interpret "not to discuss the substance of communications" with Putin with other federal officials.
And past year, the White House announced that it would stop the practice of regularly issuing readouts of phone calls between Trump and foreign leaders, which means the public has no idea how often he speaks with Putin by phone. To get to the point where those articles are written and approved by a Judiciary Committee majority (of Democrats and, ideally, constitutional-conservative Republicans), however, inquiries and investigations must proceed, hearings must be held, witnesses will nearly certainly have to be subpoenaed. Several other committees are probing related matters as well, and while many might overlap, the committee chairmen and chairwomen say they are working together on the investigations.
Sen. Mark Warner, the top Democrat on the Senate Intelligence Committee, told CNN that after hearing Cohen's testimony, "We've got to dig deeper" about the extent to which Trump pursued construction of a skyscraper in Moscow during the 2016 campaign even as he told voters he was not involved in any Russian business deals.
The probe will try to ascertain, among other things, whether Trump obstructed justice by removing perceived enemies in the Justice Department such as ex-FBI Director James Comey. Trump Press Secretary Sarah Sanders said the White House had received the letter and "the counsel's office and relevant White House officials will review it and respond at the appropriate time".
Trump and Putin met privately in Helsinki in July for more than two hours with only interpreters present.
The list of document requests also includes the National Rifle Association and Trump's embattled charitable foundation, which he is shutting down after agreeing to a court-supervised process.
Former Packers coach Mike McCarthy under investigation after berating high school referees
Although audio cannot be heard, McCarthy can be seen gesturing until the referees continued on their way and he turned and left. McCarthy coached the Packers from 2006-18, leading the team to one Super Bowl title and nine playoff appearances.
The committee is expected to use the information to amass information that officials can then comb through, according to a person familiar with the investigation. It is unclear how many will eventually be called in for interviews.
Shedding light on how partial the investigation would be, Nadler told ABC News before he issued the document requests that he's convinced that Trump has obstructed justice.
"We will act quickly to gather this information, assess the evidence and follow the facts where they lead with full transparency with the American people", Nadler said.
Trump maintains that his campaign did not collude with Russian Federation and has repeatedly attacked the investigation on Twitter. "I am an innocent man being persecuted by some very bad, conflicted & corrupt people in a Witch Hunt that is illegal & should never have been allowed to start - And only because I won the Election!" he wrote.
House Democrats took a major step in that direction Monday.
Mr. Nadler said the onslaught was necessary because Republicans, who had controlled the House until this year, let so much of the president's conduct go unchecked. "Listen to exactly what he said".