Where Mueller's disciplined silence creates a void, Trump is eager to fill that empty space with Brennan. Trump has long been unable to resist a fight with a foe who publicly challenges him, particularly on television, and Brennan got under Trump's skin with his declarations and innuendos about Trump's fitness for office and ties to Russia. But White House aides and Trump confidants say Trump's attack on Brennan is as much strategic as it is impulsive.
Goaded on by Republican Sen. Rand Paul of Kentucky, who has been fiercely critical of Brennan's policy views and actions for almost a decade, Trump signed an order weeks ago to strip the career intelligence official of his security clearance. The president has told confidants in recent days that he views Brennan as a useful adversary.
In a decision he later spelled out on Twitter, the president began attacking Brennan not just as a critic but also as a face of the institutional government corruption he believes is driving the Mueller probe, according to two Republicans close to the White House who are familiar with Trump's thinking. The two spoke on condition of anonymity because they were not authorized to discuss private conversations.
One White House official, who likewise spoke on condition of anonymity, put Trump's motivations more bluntly, saying the president simply doesn't like Brennan. "Many people don't even know who he is, and now he has a bigger voice," Trump told reporters Friday. "And that's OK with me because I like taking on voices like that. I've never respected him. I've never had a lot of respect."
Although many in the White House urged Trump to ignore Brennan, others in the president's orbit labeled the former CIA director as the epitome of the deep state that they believe has conspired to undermine Trump.
Brennan's loud criticism of Trump, including repeated accusations of "treasonous" behavior alongside Russian President Vladimir Putin last month, has caused even some allies to roll their eyes. "The common denominator among all of us that have been speaking up, though, is genuine concern about the jeopardy or threats to our institutions and values," former National Intelligence Director James Clapper, himself a frequent Trump critic, said Sunday on CNN's "State of the Union." ''But John and his rhetoric have become, I think, an issue in and of itself."
On Monday, 175 national security professionals joined 75 others before them in signing an open letter protesting Trump's decision to revoke Brennan's security clearance but indicated there is not unanimous support for how Brennan has conducted himself either.
"Our signatures below do not necessarily mean that we concur with the opinions expressed by former CIA Director Brennan or the way in which he expressed them," the letter stated. "What they do represent, however, is our firm belief that the country will be weakened if there is a political litmus test applied before seasoned experts are allowed to share their views."
Trump's fight with Brennan comes as the Mueller inquiry looks into the president's conduct in office and as Trump devotes more of his public comments and private griping to trying to undermine the investigation. It also comes amid his former campaign chairman Paul Manafort's financial fraud trial and as his lawyers engage in a back-and-forth with the special counsel's office on a potential presidential interview.
"He has become nothing less than a loudmouth, partisan, political hack who cannot be trusted with the secrets to our country!" Trump tweeted of Brennan over the weekend. "Everybody wants to keep their Security Clearance, it's worth great prestige and big dollars, even board seats, and that is why certain people are coming forward to protect Brennan," Trump said in a Monday tweet. "It certainly isn't because of the good job he did! He is a political 'hack.'"
White House officials are also preparing paperwork to revoke the security clearances of more than a half-dozen current and former national security professionals who have criticized the president or had a role in beginning the federal probe of potential collusion between Trump's campaign and agents of the Russian government.
Some Republicans close to the White House noted that in elevating Brennan, Trump was seeking to exploit partisan fractures over some of the more controversial elements in his past. While celebrated by former Obama administration officials for his role in the operation to kill al-Qaida leader Osama bin Laden, Brennan's role in the previous administration's drone program had made him a subject of some criticism from both ends of the political spectrum.
The White House has not offered specific examples of Brennan improperly using classified information. But on ABC, national security adviser John Bolton argued Sunday that Brennan politicized his information when he served under President Barack Obama.
"It was my view at the time that he and others in the Obama administration were politicizing intelligence," Bolton said. "I think that's a very dangerous thing to do." Brennan, like other former Obama administration officials, has been a prominent face on MSNBC since leaving office. Bolton is a former Fox News contributor.
Miller and Lemire reported from New York. Associated Press writers Deb Riechmann and Jill Colvin contributed to this report.