WASHINGTON (AP) — With tweets and taunts, President Donald Trump is attempting to turn one of his most outspoken critics into the public face of the Russia probe that he has long worked to discredit.

In John Brennan, the blunt former CIA director, Trump believes he has found an unsympathetic foil — one with whom he can spar publicly as he seeks to bolster his public-relations campaign against special counsel Robert Mueller and a team of federal investigators.

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 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.

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.”

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 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.”

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.”