During a recent hallway interview with Roll Call, House Oversight and Government Reform Chairman Darrell Issa (R-Calif.) stepped into an elevator that held Rep. Henry Waxman (D-Calif.).

“Henry can answer this one,” Issa said, directing to Waxman his remarks about Eric Schultz, the former aide to Sen. Charles Schumer (D-N.Y.) and current spokesman for President Barack Obama on oversight matters.

“Henry and I had the same job under different presidents. And we had the same reactions from the administrations, which is: None of them want to cooperate. It’s just not in their DNA,” Issa said. “This is the guy I pattern my work after. He’s smiling, but it’s true.”

“You are well-known as a poor imitation of me,” Waxman deadpanned.

Issa laughed and said he “doesn’t have the years of practice. I’m working on it.”

Waxman, the ranking member on the Energy and Commerce Committee, once led investigations into the administration of President George W. Bush from Issa’s current perch. But the switch in positions is no laughing matter when it comes to two GOP-led investigations that are aiming for the top levels of the Obama administration.

Waxman, for instance, harshly criticized Issa in a subsequent interview, saying, “I think Darrell Issa has a misunderstanding when he says he wants to model himself after me and seems to think that I was partisan. He’s trying to justify his own actions.”

And Rep. Elijah Cummings (D-Md.), the ranking member on the Oversight panel, blasted Issa during a recent television appearance for launching a “witch hunt.”

The two Democrats have had their hands full as House Republicans have ratcheted up their investigations into a $525 million federal loan guarantee to the now-bankrupt solar panel firm Solyndra and into the Justice Department’s Operation Fast and Furious, which resulted in assault weapons making their way to Mexican drug cartels.

Waxman and Cummings have vowed to support “fair and thorough” or “fair and responsible” investigations, respectively, but balked at subpoenas, calling them a “fishing expedition” or a “deep-sea fishing expedition,” respectively.

Rep. Diana DeGette (D-Colo.), the ranking member on the Energy and Commerce Subcommittee on Oversight and Investigations, has highlighted the role of the Bush administration on the Solyndra loan guarantee. Cummings has highlighted the role of the Bush administration on “gun walking,” the tactic at the heart of the Operation Fast and Furious matter.

On the Senate side, Schumer has also raised questions about the Bush administration’s role in approving gun walking, asking Attorney General Eric Holder about it at a Senate Judiciary Committee hearing Tuesday.

House Democrats have also used the investigations as an opportunity to plug Democratic policy priorities.

Waxman and DeGette, for instance, urged Energy and Commerce Chairman Fred Upton (R-Mich.) to expand the Solyndra investigation into examining whether the U.S. can effectively compete on clean energy internationally.

At other times, when the worst headlines hit, Waxman, Cummings and other top Democrats have gone quiet.

Last week, Lanny Breuer, assistant attorney general for the Justice Department’s Criminal Division, conceded he knew that federal officials allowed weapons to fall into the possession of Mexican drug cartels as early as April 2010, about 10 months before the department denied to Congressional investigators that the investigative strategy was used.

Breuer expressed “regret” for not alerting other top officials about the tactic when it “became public.” Cummings did not address Breuer’s admission the week it was made. Through a spokeswoman, Cummings said, “It was appropriate for Lanny Breuer to testify before Congress, and he apologized for not flagging these problematic Bush administration programs earlier.”

Republicans also flag a personnel connection among the Democrats. Dave Rapallo, a top aide to Cummings, was previously a lawyer for Obama’s National Security Council. Before that, he worked for several years for Waxman, including as his chief investigative counsel and as general counsel for the Energy and Commerce Committee.

“It’s as if they have one playbook on obstructing oversight, and both committee minorities are methodically working their way through it,” said Frederick Hill, a spokesman for Issa.

But the Democrats defending Obama from the investigations are sensitive to the need to maintain credibility.

“I’m not here to defend Solyndra. I’m not here to defend the administration,” DeGette said.

“A few months ago, I met with Brian Terry’s family. Brian Terry, of course, was a Border Patrol agent who was killed. And two guns from Fast and Furious were found at the scene. I promised them two things. One, that we would get answers for him. Two, that this would never happen again,” Cummings said Oct. 16 on CBS’ “Face the Nation.”

From the Democrats’ perspective, Republicans have so overreached on their investigations that their two duties — oversight and party — haven’t even been in tension.

“Credibility is all you really have when all is said and done on investigations,” Waxman said, referring to what he called Republicans’ lack of credibility.

“The way this investigation has been conducted, it’s been a vehicle for attacking the administration,” DeGette said, calling the scope of Upton’s request for White House documents “shocking.”

Issa “comes up with these statements, and then he goes in search of the facts,” Cummings said on “Face the Nation.”

On the question of whether the investigations had turned up anything troubling, DeGette and Waxman parted.

“We don’t have enough evidence to say,” DeGette said. But she continued, “Was this just the cost of doing business? Seems like a high cost.”

Waxman said the $525 million loss to taxpayers was part of taking risks on clean energy technology.

“It’s one of those unfortunate results that maybe can be predicted on occasion. I think most of the loan guarantees have been successful,” he said. “But there are some that are inevitably not going to be successful, and this is one of them.”