Here's how Trump plans to install longtime ally Kash Patel as FBI director

"Kash is a brilliant lawyer, investigator, and 'America First' fighter who has spent his career exposing corruption, defending Justice, and protecting the American People," Trump said in a social media post announcing his intent to nominate Patel for FBI director. 

"He played a pivotal role in uncovering the Russia, Russia, Russia Hoax, standing as an advocate for truth, accountability, and the Constitution."

Still, news of Trump's plans to nominate Patel was met with criticism - if not shock - from others in the law enforcement community. 

That's because replacing a sitting FBI director is a controversial move that breaks with the express purpose of the role, which, under post-Watergate laws, mandated that directors are nominated for 10-year terms: an express length of time designed to allow the directors - at least in theory - to operate outside political pressure or interference from a sitting president.

Trump sent shock waves through the law enforcement community in 2017 when he fired then-FBI Director James Comey, who at the time was less than four years into his 10-year term. Trump also personally selected current FBI Director Christopher Wray - whom he praised at the time as a "fierce guardian of the law and model of integrity" - to replace him.

For Trump to install Patel as FBI director, two things must happen: Wray must exit the job, and Patel must earn Senate confirmation. 

How Wray will leave remains unclear. 

He could opt to voluntarily vacate the position on his own before Trump's inauguration, though he has not yet said whether he plans to do so. If Wray does not voluntarily vacate his position, Trump could be the only president in U.S. history to have fired and installed two separate FBI directors.

Patel must also be confirmed by the Senate, though it is likely that the Republican-led chamber will move to approve him for the role.

Patel's nomination has sparked early criticism from some Democrats ahead of his confirmation hearing, who have cited his previous vows to prosecute journalists and career officials at the Justice Department and FBI that he sees as being part of the "deep state." He has since attempted to clarify some of those remarks.