By Kim Dixon and Richard Cowan
WASHINGTON, June 3 (Reuters) - What began as a bipartisan congressional probe into Internal Revenue Service practices is quickly turning into a verbal brawl with U.S. Representative Darrell Issa, no stranger to controversy, under attack from Democrats and even some of his fellow Republicans.
Issa, the California congressman who chairs the House Oversight and Government Reform Committee, on Sunday said in a CNN interview that the IRS's scrutiny of conservative groups seeking tax-exempt status was "directly being ordered from Washington."
In the same interview he accused White House spokesman Jay Carney of being a "paid liar" in his comments about the IRS and said U.S. Attorney General Eric Holder had engaged in "coverups" in other Issa probes, including the "Fast and Furious" investigation into a failed U.S. government sting operation involving gun-running.
After more than a year of investigation and accusations by Republicans that the Obama administration was lying to Congress and withholding documents, the Department of Justice inspector general last year cleared Holder of any wrongdoing in the Fast and Furious probe.
By Sunday evening, David Plouffe, a former top adviser to President Barack Obama, was rehashing via Twitter unproven allegations against Issa, partly related to his business history, that date back to 1972.
Carney responded at his regular briefing Monday that he would not get into a "back and forth" with Issa.
Representative Elijah Cummings, the senior Democrat on Issa's panel, characterized the chairman's statements on Sunday as "reckless" and "inconsistent" with the findings of an independent investigator who testified before the committee last month.
An Issa aide on Monday fired back, saying, "Mr. Cummings often makes these accusations when witness testimony disputes a high-profile narrative being pushed by this administration."
Issa's office made public only fragments of that witness testimony from unnamed IRS employees in Cincinnati. None of the fragments include quotes from any witness saying anyone in Washington ordered the targeting of Tea Party or conservative groups.
One witness, asked if "those directions emanated from Washington," responded, "I believe so."
The Treasury Inspector General for Tax Administration, whose audit is so far the only concrete evidence of misconduct at the IRS, found no evidence of White House or Washington involvement in the targeting of conservative groups by IRS workers in Cincinatti.
By Monday, some leading Republicans in Congress - Senators John McCain of Arizona and Lindsey Graham of South Carolina - were taking to the airwaves to gently warn Issa to tone down the attacks.
As the chairman of a House committee with broad investigative powers, or earlier as its senior Republican when Democrats controlled Congress, Issa has established a deep record of leveling accusations against the White House and of demanding reams of documents that then become minefields for the Obama administration.
THE HUNT FOR EMAILS
In early 2010, as the senior Republican on the oversight committee, Issa slammed the Federal Reserve Bank of New York for not immediately turning over all of its email traffic about $62.1 billion in payments related to the bailout of insurance giant AIG.
And a year ago, while again demanding a large volume of internal communications, Issa accused Obama or his aides of obstructing an investigation into the botched "Fast and Furious" gun-running probe on the Arizona border with Mexico.
Besides the IRS investigation, Republicans also are spearheading probes into the Obama administration's handling last September of an attack on the U.S. diplomatic mission in Benghazi, Libya, and the Justice Department's tracking of telephone conversations of Associated Press reporters.
Issa's committee also has a leading role in the Libya affair and he has made public statements linking all three matters.
"I will work with my fellow House Chairmen on an appropriate response to Obama administration officials," Issa said last month of the media snooping issue.
While Republicans in Congress see the probes as girding their long-held argument that the administration cannot be trusted to govern honestly and efficiently, there are worries the public could get turned off by a preoccupation with investigations rather than cooperative work to improve the economy.
"There is a concern broadly, about any of the three investigations, that we don't overplay our hands," a House Republican leadership aide said.
"The general consensus on the street is at times Darrell Issa is a lightning rod and sometimes his investigations tend to look like partisan witch-hunts and that can hurt the party," said Ford O'Connell, a Republican strategist who worked on McCain's 2008 presidential bid and advises mostly moderate Republicans. (Additional reporting by David Lawder; Writing by Richard Cowan; Editing by Fred Barbash, Martin Howell and Jim Loney)