Politico finally seriously notices the Gunwalker scandal.

Josh Gerstein and Jake Sherman write at Politico: "Darrell Issa, Department of Justice feud heats up."

The Obama administration and Rep. Darrell Issa seem to be headed for their biggest showdown yet as the House oversight committee chief prepares for a Wednesday hearing into an undercover, federal gunrunning investigation that lost track of weapons later found at the scene of a Border Patrol agent’s murder in Arizona.

Issa, a California Republican, contends the administration has stonewalled his requests for records about a deeply flawed investigation, known as “Operation Fast and Furious,” that may have allowed hundreds of weapons from U.S. gun dealers to flow across the border to Mexican drug gangs. Issa also says congressional Democrats are “obstructing” his inquiry into what he calls “reckless and inappropriate decisions by top Justice Department officials.”

Justice Department officials say handing over sensitive documents to Congress could imperil pending prosecutions, including the case involving the murder of Border Patrol Agent Brian Terry and the prosecution of 20 people as a result of the gunrunning probe.

Administration aides fear the dispute could escalate to produce a rare House vote to cite Justice officials for contempt. That, in turn, would likely trigger a court battle testing Congress’s rights to delve into ongoing criminal investigations.

Administration officials also charge that Issa and Sen. Charles Grassley (R-Iowa) released highly confidential information about the identity of a former target of the probe and his dealings with an informant working with the Bureau of Alcohol, Tobacco, Firearms and Explosives.

Issa insisted that the fault for any mistakes lies with the Justice Department because it has moved slowly and handed over few records since he served the agency with a subpoena on March 31.

“If the administration started cooperating then, the errors that may occur would not occur,” Issa told POLITICO in an interview Monday. “As long as they don’t cooperate, any errors we make are on them, not on us.”

“We do not have a dialogue — they’ve asked for permission to redact what we have, but in fact they won’t give us that same information. If they would deliver all the information full and complete with the suggested redactions, we could probably agree to virtually all or all of the redactions,” Issa said. The Justice Department handed over hundreds of documents Monday evening, but a Republican committee aide said the panel wants more.

Democrats, led by Elijah Cummings of Maryland, the top Democrat on the committee, don’t object to investigating the controversial ATF operation — in fact, many say they support the congressional probe. But Cummings, a lawyer from Baltimore, says he wants to proceed with hearings after the federal government completes its prosecutions.

“It is extremely important to me that we maintain the integrity of this committee,” Cummings said in an interview. “And part of that is trying to consistently do everything in our power to avoid doing anything prejudicial to particularly a criminal trial. We can have the committee achieve what it needs to achieve, but at the same time, not prejudice these cases.”

Issa insisted his investigation “has no overlap” with the crimes the federal government is investigating and the murder trial that’s slated to start in the coming months. He called Cummings’ issues “without any foundation or basis,” adding that Cummings “has been part of the deliberative obstruction by the administration.”

“Is it timely? Yes.” Issa said of the hearing and investigation. “Americans are at the risk of dying from those weapons today. And the prosecution of 20 people who bought these has nothing to do with this investigation.”

When asked if the timing could be altered, Issa deadpanned, “Iran-Contra could’ve been done at a later date. Watergate could’ve been done at a later date.”

The dispute is expected to heat up Wednesday as the Justice Department’s top liaison to Congress, Assistant Attorney General Ron Weich, testifies to the oversight panel.

According to sources familiar with his testimony, Weich — a former top aide to Senate Majority Leader Harry Reid (D-Nev.) — plans to claim that Issa’s subpoena of a witness expected to testify at the trial prompted a defendant in the case to back out of a meeting to discuss a potential plea bargain. The defendant’s lawyer cited fears that any disclosures at the meeting with prosecutors might become public as a result of the congressional probe, the sources said.

Administration officials say they’ve given Issa hundreds of pages of documents, are allowing staff to look at more sensitive records at the Justice Department, and are searching through what may be a million pages of documents responsive to the House’s requests. However, Justice Department officials also say they’re withholding some sensitive details about the investigation.

Issa also subpoenaed documents from the administration that the committee already has received from whistleblowers — an attempt to test the cooperation of the administration and integrity of what the committee has obtained, committee insiders say.

Democrats are furious about how Issa has handled the investigation.