John Bolton, welcome to the Resistance?

And the longer Bolton takes to speak out, some add, the more the skepticism of his motives will rise.

“There is an early mover advantage for witnesses to come forward on presidential misconduct, not to mention a constitutional duty to do so,” said Jeffrey Prescott, a former senior official in the Obama administration. “Soon, the question for those around Trump, including those who have left the administration, is ‘If you saw something, why didn’t you say something?’”

John Gans, author of “White House Warriors,” a book about the NSC, noted that Bolton, a Yale-trained lawyer, has long held a view that the president has expansive power on foreign policy. Republicans seeking to shut down the inquiry will be relying in part on arguments he and others have made, Gans said.

“The question for all those who see Bolton as the key to bringing Trump down is whether he will abdicate or put aside his long-held views on the presidency,” Gans said.

Taylor’s testimony Tuesday also raised questions about the actions of two other Trump aides: Secretary of State Mike Pompeo and Tim Morrison, a top NSC official.

According to Taylor, he spoke privately in late August with Bolton about his concern that Trump was withholding U.S. military assistance to Ukraine, though this was before he realized the aid freeze may have been to pressure Zelensky into pursuing the investigations.

On Bolton’s advice, Taylor sent a first-person cable to Pompeo, sharing his worries that withholding the aid would hurt Ukraine’s ability to defend itself against Russia.

“I told the secretary that I could not and would not defend such a policy,” Taylor said. “Although I received no specific response, I heard that soon thereafter, the secretary carried the cable with him to a meeting at the White House focused on security assistance for Ukraine.”

The testimony deepens the mystery surrounding Pompeo’s actions throughout the affair. He has acknowledged being on the July 25 call, but he’s been silent on what he knew, when he knew it and how he could have permitted Giuliani and others to play such a major role in Ukraine policy.

The State Department did not reply to a request for comment.

Morrison is an arms control expert who took over from Hill as a senior NSC official dealing with Europe and Russia. Taylor’s testimony relies on what he said Morrison relayed to him about several key events.

Those events include the July 25 call — which Taylor was not on, and which Morrison said “could have been better.”

It also included Morrison’s account of a conversation between Sondland and a Ukrainian representative in Warsaw, in which Sondland said the military assistance wasn’t coming unless Ukraine committed to pursuing the investigations Trump wanted.

Morrison didn’t reply to a request for comment. He’s long been associated with Bolton, but he has stayed at the NSC even after Bolton’s departure.

House Democrats have asked Morrison to testify, but it’s not yet known whether he will do so, given the White House refusal to cooperate with the impeachment inquiry.