Special Counsel Jack Smith’s defiant rejoinder to Republican lawmakers puts in sharp relief the growing rift between the prosecutor and President Trump’s party — a conflict that could soon ratchet up with the issuance of a subpoena to the prosecutor.

The latest salvo came in a letter to Senator Charles Grassley, 92, from Mr. Smith’s lawyers, Peter Koski and Lanny Breuer, both partners at the Covington & Burling. The attorneys argue that “While Mr. Smith’s prosecutions of President Trump have predictably been politicized by others, politics never influenced his decision making.”

Messrs. Koski and Breuer accuse Mr. Trump of “attempting to overthrow the results of the 2020 election” and drafted their letter as a riposte to a growing firestorm that centers on the recent discovery that during the Biden years, Mr. Smith secretly obtained the telephone data of eight GOP senators and one member of the House of Representatives from the days around January 6, 2021. Mr. Smith obtained that information as part of his “Arctic Frost” investigation into efforts to overturn the results of the 2020 election.

Earlier this month, Mr. Grassley’s office disclosed the existence of that probe. A Republican congressman, Jim Jordan, has written his own letter to Mr. Smith summoning him to testify before the House Judiciary Committee and contending that the prosecutor’s sworn account “is necessary to understand the full extent to which the Biden-Harris Justice Department weaponized federal law enforcement.” Mr. Jordan accuses Mr. Smith of compromising  the “integrity of the criminal justice system.”

Mr. Smith’s lawyers, though, argue that his pursuit of the telephone records “was entirely proper, lawful, and consistent with established Department of Justice policy.” The special counsel, they explain, obtained only “telephonic routing information — collected after the calls have taken place — identifying incoming and outgoing call numbers, the time of the calls, and their duration. Toll records are historical in nature, and do not include the content of calls.”

Mr. Smith’s findings were accumulated between January 4, 2021, and January 7, 2021 — meaning that they focused on the events of January 6. He was trying to “confirm or refute reports by multiple news outlets that during and after the January 6 riots at the Capitol, President Trump and his surrogates attempted to call Senators to urge them to delay certification of the 2020 election results.”

Mr. Smith’s team maintain that “it is well established that obtaining telephone toll records pursuant to a subpoena is a routine and lawful investigative step that does not violate an individual’s expectation of privacy.” That expectation is protected by the Fourth Amendment, which ordains that the “right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated.”

The director of the FBI, Kash Patel, has claimed that Mr. Smith put the information relating to the surveillance effort in a “lockbox in a vault, and then put that vault in a cyber place where no one can see or search these files.” Mr. Smith’s lawyers write here that “It is not clear what cyber place in a vault in a lockbox Director Patel is describing, but Mr. Smith’s use of these records is inconsistent with someone who was trying to conceal them.”

Messrs. Koski and Breuer note that Mr. Smith referenced the telephone data in both his indictment of Mr. Trump and in his final report on the January 6 case. In that dossier the special counsel argued that “but for Mr. Trump’s election and imminent return to the Presidency, the Office assessed that the admissible evidence was sufficient to obtain and sustain a conviction at trial.”

That was Mr. Smith’s final word on the matter for months, but in recent weeks the prosecutor has stepped back into the public eye. In a keynote address at George Mason University last month he declared that “what I see happening at the Department of Justice today saddens me and angers me …  the government, using the vast powers of the criminal justice system to target citizens for exercising their constitutional rights.”

In a  conversation in Britain with paid MSNBC contributor Andrew Weissman, a former top deputy to Special Counsel Robert Mueller, earlier this month, Mr. Smith blasted as “ludicrous” the notion that his prosecutions of Mr. Trump were political in nature. He also argued that “nothing like what we see now has ever gone on” at the Department of Justice. 

Mr. Smith  also appeared in a video produced by a group opposed to Mr. Trump’s firing of DOJ personnel. Mr. Smith’s whole team  — who volunteered for duty in 2022, when the prospect of a return to power for Mr. Trump seemed fanciful at best —  has since been terminated.

The escalation of rhetoric toward Mr. Smith from GOP lawmakers could presage the issuance of a subpoena summoning the prosecutor to testify under oath. If he declines, the House of Representatives could vote to hold him in contempt. It would then fall to the DOJ to press criminal charges. During President Biden’s administration two senior advisers to Mr. Trump, Stephen Bannon and Peter Navarro, were both convicted of contempt and spent some four months in prison. 

Mr. Smith, who lived abroad at the Hague before his assignment to prosecute Mr. Trump, was last spotted in England  — which has an extradition treaty with America.