The deal struck by District Attorney Alvin Bragg to allow his one-time deputy, Mark Pomerantz, to testify before Congress next month inaugurates an age of anxiety for both Mr. Bragg and the lawmakers cum inquisitors who will question Mr. Pomerantz. It revolves around one question: What will he say?

No friend of Mr. Bragg or President Trump, Mr. Pomerantz resigned in protest from his unpaid position in Mr. Bragg’s office last year after the Manhattan district attorney passed on prosecuting Mr. Trump for financial crimes. He went on to write a book denouncing Mr. Bragg’s failure to prosecute Mr. Trump, whom he called a criminal. 

Now that Mr. Bragg has abruptly changed course and decided to prosecute Mr. Trump over the sordid Stormy Daniels saga, House investigators want to hear from Mr. Pomerantz, whose testimony could open a Pandora’s box of criticisms of the embattled district attorney.

The Sun spoke to a legal legend, Harvey Silverglate, who wished a “pox on everyone’s house,” by which he meant Messrs. Bragg and Pomerantz and Mr. Trump himself. He called Mr. Bragg’s prosecution of the former president “insane” and the accompanying indictment the “strangest” one that he has ever seen in more than 50 years of practicing law.  

Mr. Silverglate, a longtime defense lawyer, opined that “a lot of prosecutors want to be the one to put Mr. Trump in jail.” By bringing charges, Mr. Bragg now jumps to the front of the queue, which also includes the special counsel, Jack Smith, as well as the district attorney of Fulton County in Georgia, Fani Willis.   

That Mr. Pomerantz will speak at all is a victory for Representative Jim Jordan and his fellow Republican lawmakers on the House Judiciary Committee, and a vindication of their position that Congress has an interest in the prosecution of Mr. Trump. Now, all eyes are on the story that Mr. Pomerantz plans to tell.  

Mr. Bragg had sought to fight that testimony on federalism grounds, claiming that Congress’s snooping around his indictment would be an affront to the federalism of the Framers. That tack was rejected by a federal district court judge, Mary Kay Vyskocil, who ruled that “no one is above the law,” including Mr. Bragg himself.

While the riders of the Second United States appeals circuit paused that order temporarily, Mr. Bragg’s deal with Mr. Jordan short-circuited a more considered treatment from that circuit or, potentially, the Supreme Court. Mt. Bragg likely assessed that such a trajectory would not bend in his favor. 

The district attorney is framing the agreement allowing Mr. Pomerantz to testify on May 12 as a victory, and one that “ensures any questioning of our former employee will take place in the presence of our General Counsel on a reasonable, agreed upon timeframe.”  

Whenever Mr. Pomerantz testifies, it will not be the first time that he has opined on the case since he abruptly left Mr. Bragg’s office last summer. He was first hired, on a pro bono basis, by the district attorney’s predecessor, Cyrus Vance Jr. Mr. Silverglate notes that that arrangement indicates a “prosecutorial zeal” that leaves him “nervous.”

In March of last year Mr. Pomerantz headed for the exit with a colleague, Carey Dunne, to protest Mr. Bragg’s then-recalcitrance in charging the former president. Mr. Pomerantz issued a scathing public letter as he exited, and it set him against both his former boss and the former president.  

In that letter and the subsequent book, “People vs. Donald Trump: An Inside Account,” Mr. Pomerantz wrote, “I believe that Donald Trump is guilty of numerous felony violations of the penal law.” He wrote that he feared that Mr. Bragg’s “decision means that Mr Trump will not be held fully accountable for his crimes.” Mr. Bragg initially sought to block the book’s publication, without success. 

Indeed, Mr. Bragg was none too happy with Mr. Pomerantz’s loquaciousness, saying of the rogue lawyer, “It is appalling that he insulted the skill and professionalism of our prosecutors,” adding that “we have the most outstanding lawyers in the country working every day” to “keep our city safe from the streets to the suites.”

The indictment that was eventually handed up, centered on the hush money payments to the porn star Stormy Daniels, is not the kind of accountability that Mr. Pomerantz had in mind; he calls that line of prosecution a “zombie case,” which is likely music to Mr. Jordan’s ears. 

Mr. Pomerantz attracted criticism from Mr. Trump, who called him “deranged,” as well as from the president of the District Attorneys Association of the State of New York, J. Anthony Jordan, who accused Mr. Pomerantz of “upending the norms and ethics of prosecutorial conduct potentially in violation of New York criminal law.” 

Mr. Pomerantz reserved special scorn for Mr. Bragg, mixing his transportation metaphors to call the case against Mr. Trump “the legal equivalent of a car crash” and accusing the district attorney of a “pilot error.” Mr. Bragg shot back that “Mr. Pomerantz’s plane wasn’t ready for takeoff.”