POLITICAL INSULATION

Cordero, now the director of national security studies at Georgetown University Law Center, said it would be unthinkable for prosecutors to bow to recent media criticism.

"The Justice Department is by tradition supposed to be politically insulated when it's conducting an investigation, and I don't see any reason why that would change now - as unpopular as it might be," she said.

Holder's political standing has been on a slow decline. On Friday Senator Joe Manchin of West Virginia became the highest-profile Democrat to suggest he should step down.

Manchin said that even if a public official like Holder has good intentions, "if they're not being effective and they're not being received, how effective is it and how good is it for the country?"

White House senior adviser Valerie Jarrett backed Holder in a separate interview on Thursday, telling The Huffington Post that Holder "will be in his position for quite a while."

Chris Harper, a journalism professor at Temple University, said Holder might need to consider handing off the leak investigations.

"It is the fox guarding the chicken house. It's time to start considering special prosecutors in these cases," Harper said.

Holder in June 2012 handed off two leak probes to the chief federal prosecutors in Washington, DC, and Maryland, although both prosecutors still answer to either Holder or his politically appointed deputy, James Cole.

CHANGES SOUGHT

One change in Justice Department procedure sought by media outlets is an opportunity to contest in advance any demand for records such as telephone call lists. The Associated Press reported on May 13 that the Justice Department seized some of its phone records without giving the news agency a chance to object beforehand.

Prosecutors are trying to find out who said about a foiled plot to bomb an airliner over US soil.

Journalists also are pressing that they not be labeled as possible criminals, as when an FBI agent in a search warrant affidavit used the term co-conspirator to describe Fox News reporter James Rosen. Rosen, who was not prosecuted, had reported secret views of US intelligence officials about North Korea.

Holder as recently as Friday continued to express displeasure at the methods his prosecutors used to pursue records from Fox News and the Associated Press, said Leslie, who with other press advocates met Holder.

"He seemed to sincerely believe that those incidents were handled in a way that he didn't like," Leslie said.

Glenn Greenwald, the lead author of the Guardian's surveillance stories, said that he expects a US investigation and upgraded the security measures on his computer in Brazil, where he lives, as a precaution.

Greenwald added on Twitter, "Dear DOJ: your bullying tactics will scare some sources, but they embolden others."