The next phase of the impeachment inquiry into President Trump will take place Thursday when the embattled acting director of National Intelligence testifies on Capitol Hill.

Lawmakers will grill spymaster Joseph Maguire over his weeks-long delay in turning over a whistleblower complaint to Congress, leading once-cautious House Democrats to launch an impeachment inquiry and igniting a political firestorm.

Rep. Jim Himes (D-Conn.) predicted the open hearing “will probably be waste of time,” since the sensitive substance of the complaint can’t be discussed in public.

But the House Intelligence Committee member added the hearing would likely be “embarrassing” to Maguire because he’ll “have to justify unjustifiable actions.”

Speaker Nancy Pelosi (D-Calif.) specifically cited Maguire’s delays in her speech announcing the inquiry on Tuesday, calling it “a violation of law.”

The White House finally provided the classified complaint to top lawmakers late Wednesday.

Little is publicly known about the still-classified complaint, except that it referenced a phone call between Trump and Ukrainian president Volodymyr Zelensky.

A detailed summary of the call released by the White House on Wednesday showed Trump requesting Zelensky to probe a son of former Vice President Joe Biden, Hunter Biden.

Trump has said the call was “perfect,” while House Intelligence Committee chairman Rep. Adam Schiff (D-California) called it a “classic Mafia-like shakedown of a foreign leader.”

The unknown whistleblower who filed the complaint wants to speak to Congress, Schiff said.