Updated at 5:07 p.m. ETThe top Democrat on the House Oversight Committee is demanding an explanation of President Trump's decision this week to revoke the security clearance of former CIA Director John BrennanIn a letter to White House chief of staff John Kelly, Rep. Elijah Cummings, D-Md., asked for a detailed briefing on the decision and suggested Trump may have failed to follow proper procedures.Brennan himself also pushed back against the president's move, calling it "desperate" and "politically motivated."The public spat highlights the increasingly partisan shadow that has been cast over national security and intelligence in the Trump era.The administration has offered conflicting explanations for the president's decision. Trump's initial statement pointed to what the president called Brennan's "erratic conduct and behavior," a standard that Cummings challenged."If making 'outrageous' statements or engaging in 'wild outbursts on the Internet and television' were grounds for denying access to classified information, many of the President's top aides — indeed, perhaps even the President himself — would be swept into this unprecedented new category," the congressman wrote.Trump later pointed to Brennan's role in investigating Russia's interference in the 2016 presidential election. Brennan helped lead that probe as CIA director in the Obama administration. Trump blames Brennan and others for planting the seeds of the special counsel's probe that has dogged his presidency for the past 15 months."I call it the rigged witch hunt," Trump told the Wall Street Journal. "And these people led it."Trump said that's why he wanted to strip Brennan of his security clearance. "I think it's something that had to be done," he told the Journal.There was no suggestion that Brennan has leaked classified information.The White House is also reviewing the security clearance of other former officials who have been critical of the president, including former Director of National Intelligence James Clapper, former National Security Agency Director Michael Hayden and former FBI Director James Comey.Former high-ranking officials typically retain their security clearance when they leave office so their successors can consult with them on sensitive issues.In an op-ed for the New York Times, Brennan argued the decision to strip his security clearance and review others' is designed to muzzle the president's political opponents."Mr. Trump clearly has become more desperate to protect himself and those close to him," Brennan wrote, calling the clearance revocation "an attempt to scare into silence others who might dare to challenge him."Hayden made a similar suggestion in an interview with CNN."The White House just messaged the entire American intelligence community," Hayden said. "If you stand up and say things that upset the president or with which he disagrees, he will punish you. And that is a horrible message to be sending to folks who are there to tell you objective truth."The move by Trump seemed not to have its apparent intended effect on William McRaven, a retired Navy admiral who oversaw the raid that killed Osama bin Laden during his time commanding U.S. special operations forces in the Obama administration. In an open letter to Trump published online Thursday afternoon by the Washington Post, McRaven defended Brennan.The former CIA director "is one of the finest public servants I have ever known," McRaven wrote. "Few Americans have done more to protect this country than John. He is a man of unparalleled integrity, whose honesty and character have never been in question, except by those who don't know him." McRaven continued: "Therefore, I would consider it an honor if you would revoke my security clearance as well, so I can add my name to the list of men and women who have spoken up against your presidency. "The decision to revoke Brennan's security clearance drew a mixed reaction from Trump's fellow Republicans.Sen. Bob Corker, R-Tenn., who chairs the Foreign Relations Committee, said he was bothered by the president's move."It feels very much like a banana republic kind of thing," Corker said.Other lawmakers were less sympathetic to Brennan.In a statement issued Thursday in response to Brennan's op-ed in the New York Times, Sen. Richard Burr, R-N.C., chairman of the Senate intelligence committee, suggested the president's decision to revoke Brennan's security clearance could be well within his "full authority" in some circumstances: