Rep. Darrell Issa (R-Calif.), chairman of the House Committee on Oversight and Government Reform, is leading the Republican charge against the Obama administration over the IRS scandal and the White House's handling of Benghazi. But after Issa referred to President Obama's spokesman, Jay Carney, as a "paid liar" on Sunday talk shows, aides to congressional GOP leaders quietly urged him to drop the personal attacks.

The GOP watchdog is sticking to his guns, though, telling Politico that the administration's explanation of the scandals has changed as the truth drips out. "The White House has tried to vilify me," Issa says, "rather than getting into the facts."

Issa's unpredictability is reportedly starting to worry his allies. John Bresnahan and Jake Sherman at Politico say that Republicans are afraid that Issa's attack-dog style "could jeopardize the biggest gift handed to them in months — public outrage over the IRS scandal, combined with questions over Benghazi. They think Issa should stop personalizing the scandals by insulting Obama and his aides and focus on the facts."

Some observers think it's too late for Issa to dial it down. Joe Gandelman at The Moderate Voice says Issa already has credibility problems. He's known for declaring that he'll hold hearings that will "bust the town wide open," Gandelman says, but it's usually the hearings that are a bust.

Issa isn't acting as if he's stewarding a committee in a great institution seeking to learn the truth. He's acting like a hyper-partisan with investigative powers who has already judged and desperately seeks something on the other party. He has not proven a thing yet. And, in the process, he’s destroying his own credibility — and the seriousness of questions raised about the IRS.

Which should worry a lot of Republicans. And please the White House. [Moderate Voice]

Not everyone's convinced Issa is doing the GOP cause any harm. John Dickerson at Slate notes that Democrats are arguing that Republicans are overreaching with these controversies, especially with some hardline conservatives suggesting Obama deserves impeachment. But, Dickerson says, "Republicans have not overplayed their hand. Unlike the late 1990s, they have the country with them in their pursuit of answers."

Americans want to get to the bottom of the IRS mess, the issue that has prompted some of Issa's extravagancies. New revelations, like this week's disclosures about IRS profligacy, are offering fresh reasons for outrage, and the disciplining of two IRS officials for receiving gifts against ethics rules ratifies the investigations. New polls show that the country thinks the president is less trustworthy, so the chances the public will rush to his defense against the meanies going after him is shrinking...

The long-term danger for Chairman Issa may not be overreach but ineffectiveness. When you overhype evidence, people will notice if you don't have the goods, and ultimately you lose credibility. But we are a long way from that. Right now, the public wants Republicans to make their case. [Slate]