The lawyer Mark Zaid has represented a wide array of whistle-blowers, both Republicans and Democrats, during multiple administrations. But it was his involvement with the whistle-blower at the center of the first impeachment case against President Trump that drew the president’s ire.

While at a wedding last weekend, Mr. Zaid learned through an interview Mr. Trump gave to The New York Post that his security clearance would be revoked, a move that could jeopardize his ability to represent officials who work on classified matters. He still has received no formal notification or explanation.

“I’m doing the same thing I have done since the day I set foot in Washington, D.C., 32 years ago,” Mr. Zaid said. “All I do is hold the administration — whoever that is, Republican or Democrat — accountable for unlawful and ethical lapses.”

“It is more than obvious that Trump is fulfilling the promises that he made and campaigned on, that he would retaliate against those who did him wrong,” he added.

Mr. Zaid is on what has become an ever-growing list of President Trump’s perceived enemies. Through the first month of his administration, Mr. Trump and his allies have carried out a campaign of revenge and retribution that has little analogue in American history.

He has pulled protective details from former colleagues facing death threats from Iran. He has revoked or threatened to revoke the security clearances of President Biden, members of his administration and dozens of others. His administration has taken steps to target members of the media seen as unfriendly, taken the hatchet to entire agencies perceived as too liberal and fired or investigated government workers deemed disloyal.