"The four individuals we've subpoenaed today advanced unsupported theories about election fraud, pushed efforts to overturn the election results, or were in direct contact with the former President about attempts to stop the counting of electoral votes," Committee Chair Bennie Thompson said in a statement.
The statement accused Giuliani and Powell of playing a role in undermining confidence in the results of the 2020 presidential election.
Thompson said that Giuliani "was reportedly in contact with then-President Trump and various Members of Congress regarding strategies for delaying or overturning the results of the 2020 election."
He went on to say that Powell "urged President Trump to direct the seizure of voting machines around the country to find evidence that foreign adversaries had hacked those machines and altered the results of the election."
The committee also said that Ellis and Epshteyn were involved with efforts to stop Congress from certifying the results of the election during a joint session on January 6.
The statement said that Ellis reportedly drafted "two memos purporting to analyze the constitutional authority for the Vice President to reject or delay counting electoral votes."
The committee said that it is seeking more information about a reported call that Epshteyn had "with former President Trump on the morning of January 6th to discuss options to delay the certification of election results in the event of Vice President Pence's unwillingness to deny or delay the certification."