One of President Trump’s most reliable Senate allies has vowed to probe whether Justice Department and FBI brass considered an “attempted bureaucratic coup” to oust the commander-in-chief.

“I think everybody in the country needs to know if it happened,” South Carolina’s Lindsey Graham, chair of the Senate Judiciary Committee, told CBS News Sunday.

Graham called ex-FBI Deputy Director Andrew McCabe’s revelation that top officials discussed invoking the 25th Amendment to force Trump out for supposedly being unfit for office “beyond stunning.”

Graham also said he would subpoena ex-FBI Director James Comey — whose firing prompted McCabe to open a counterintelligence investigation into the president — and Deputy Attorney General Rod Rosenstein to get to the bottom of their actions.

McCabe said in an interview that aired Sunday that a “crime may have been committed” when Trump fired Comey and tried to publicly undermine the probe into his campaign’s many ties to Russia.

McCabe also said the FBI had good reason to open a counterintelligence investigation into whether Trump was in cahoots with Russia, and therefore a possible national security threat, following Comey’s May 2017 firing.

“And the idea is, if the president committed obstruction of justice, fired the director of the FBI to negatively impact or to shut down our investigation of Russia’s malign activity and possibly in support of his campaign, as a counterintelligence investigator you have to ask yourself, ‘Why would a president of the United States do that?’ ” McCabe said.

“So all those same sorts of facts cause us to wonder is there an inappropriate relationship, a connection between this president and our most fearsome enemy, the government of Russia?”

McCabe was fired from the Justice Department last year after being accused of misleading investigators during an internal probe into a news media disclosure.

The allegation was referred to the US Attorney’s Office in Washington for possible prosecution, but no charges have been brought.

With AP