Special Counsel Jack Smith’s launching of a new law firm with three other former prosecutors brings into focus the next chapter  — a potentially lucrative one —  in the longtime government lawyer’s legal career.

Mr. Smith will be joined by the attorneys Tim Heaphy, David Harbach, and Thomas Windom, the latter two of whom served under the special counsel during his prosecution of President Trump for alleged election interference and the storage of classified documents at Mar-a-Lago. The creation of the new firm, which is expected to open for business next month, was first reported by the Times.

It is not yet known how much Mr. Smith will charge for his services. Mr. Heaphy, while not on that team, was the lead investigative lawyer for the House January 6 committee. That tribunal, dominated by Democrats, ultimately ended up referring Mr. Trump for criminal prosecution. Mr. Heaphy declares in a statement that the embryonic firm will be guided by “integrity, commitment, and zealous advocacy” for its clients.

Messrs. Smith and Windom are both facing scrutiny from congressional Republicans in the wake of their pursuit of criminal convictions against Mr. Trump. Mr. Windom, who served as senior assistant special counsel under Mr. Smith, has been criminally referred to the Department of Justice by the chairman of the House Judiciary Committee, Congressman Jim Jordan. Mr. Jordan contends that Mr. Windom refused, with no compelling justification, to answer questions under oath.

Mr. Smith has also locked horns with Mr. Jordan. In the latest salvo between the two men, the lawmaker issued Mr. Smith a subpoena to produce documents by December 12 and to appear for closed door questioning under oath on the morning of December 17. Mr. Smith had previously declared in a letter of his own that he would testify only in a public hearing and if he were also granted immunity.

Congressional Republicans are particularly eager to grill Mr. Smith over “Operation Arctic Frost,” his probe into Mr. Trump’s effort to stay in power after the 2020 election. As part of that investigation Mr. Smith surveilled telephone metadata from 10 Republican senators and one GOP congressman. The warrants to access that information were in almost every case accompanied by “do not disclose” orders, meaning that the solons were unaware they were being observed. 

Senator Chuck Grassley calls the surveillance of lawmakers an “unconstitutional breach.” He has released correspondence between Mr. Smith’s team and the DOJ that appears to indicate that Main Justice had at least momentary misgivings about the “litigation risk” that such surveillance could pose given the absolute immunity the Constitution offers to lawmakers when they are acting within the sphere of legislative activities. 

The special counsel, who was prosecuting war crimes at the Hague at the time he was appointed by Attorney General Merrick Garland two days after Mr.Trump declared his intention to regain the White House, is himself represented by Peter Koski and Lanny Breuer of the Covington & Burling law firm. Disclosures Mr. Smith made before he resigned showed that Covington provided him some $150,000 in pro bono legal services while he was special counsel.

Mr. Smith’s legal resume was robust enough for Mr. Garland to select him to pursue two of the the highest profile cases in American history — the two against Mr. Trump — but does not include confirmation by the Senate. That proved to be a decisive lacuna when the presiding judge in the Mar-a-Lago case, Aileen Cannon, ruled that his appointment lacked legal ballast. She dismissed the charges against Mr. Trump and his co-defendants. Mr. Harbach worked on that case alongside Mr. Smith.

The special counsel has come under some scrutiny for his own legal judgment in the Mar-a-Lago case, most notably his decision to seek an indictment in South Florida rather than the District of Columbia. One of Mr. Smith’s deputies, David Raskin, is reported by the Washington Post to have responded “Are you all f—ing insane?” when he was told that the case would proceed in the Sunshine State. Mr. Raskin reportedly warned that the possibility of drawing Judge Cannon was an “existential threat to the case.”

Mr. Trump’s victory over Vice President Harris led to the dismissal of both of Mr. Smith’s cases — the Department of Justice’s position is that sitting presidents are “categorically immune” from federal prosecution. The  election interference prosecution, though, was upended even earlier than that when the Supreme Court ruled in Trump v. United States that, contra Mr. Smith, official presidential acts are presumptively immune from prosecution. 

Even as Mr. Smith’s cases faltered, the special counsel has maintained a defiant attitude. In his final report on the January 6 case he contends that “but for” Mr. Trump’s reelection, the evidence adduced would have been more than sufficient to not only try Mr. Trump, but also to convict him. In September Mr. Smith declared in a keynote address that  “what I see happening at the Department of Justice today saddens me and angers me.”

Mr. Smith has ventured that “the idea that politics would play a role in big cases like this is absolutely ludicrous.” That comment came in a discussion at London with MS Now contributor — and former deputy to Special Counsel Robert Mueller — Richard Weissmann.  Mr. Smith is also facing scrutiny into allegations from Senator Tom Cotton that the timing of his prosecutions violated the Hatch Act, which bars federal employees from undertaking some activities that could affect elections.