Investigations into the Internal Revenue Service's targeting of conservative groups present a golden political opportunity for Republicans to score points against the White House and attempt to link President Barack Obama to political scandals. But as the House holds three separate hearings on the IRS this week, it's unclear how far their attacks can go before they backfire.

On Tuesday, the House will hold its second hearing of the week to hear from tea party groups targeted by the IRS. But in gearing up for a series of three hearings in the House this week, one top Republican went so far in attacking Obama that he received pushback from within his own party.

After weeks of holding back, Rep. Darrell Issa, R-Calif., on Sunday accused the White House of being directly involved in the decision by employees in the IRS’s Cincinnati, Ohio, office to investigate tea party groups. On Monday, even some of his fellow Republicans thought he had gone too far.

“As late as last week, the administration's still trying to say there's a few rogue agents in Cincinnati, when in fact the indication is they were directly being ordered from Washington,” Issa, who chairs the House Oversight Committee, said on CNN show “State of the Union.” He went on to call White House spokesman Jay Carney a “paid liar” for suggesting otherwise.

When asked about Issa’s “liar” comment, Sen. John McCain, R-Ariz., was much more measured. “I never like to use that word,” McCain said Monday on “CBS This Morning.” “I think we should let the investigation take its course and let the facts come out. ... I think these hearings are what we should rely on to a significant degree.”

Sen. Lindsey Graham, R-S.C., shared a similar sentiment on Fox News radio Monday. "I don't believe this was something thought up in the Cincinnati office, but I have no evidence that goes to the White House,” Graham said, according to the Huffington Post. With regard to the "liar" comment about Carney, Graham cautioned that "you can go too far" with personal attacks. 

Seemingly addressing Issa, Graham said, “Put the puzzle together, and let the American people make their own judgment.”

On Monday, a subcommittee of the House Appropriations Committee on financial services grilled the newly appointed acting commissioner of the IRS, Danny Werfel, and Treasury Inspector General J. Russell George, who authored the initial report on the wrongdoing at the Cincinnati office. 

At Monday’s hearing, Republican lawmakers were moving away from Issa’s combative tone, partly because neither of the witnesses was at the IRS when the Cincinnati office was investigating tea party groups. Though Werfel endured sharp questioning from several Republicans, he also proved adept at deflecting Republican members’ more accusatory questions by promising to clean house at the IRS.

Tuesday’s Ways and Means Committee hearing will focus on the representatives of six tea party groups. And on Thursday, Issa will return to the spotlight when his House Oversight and Government Reform Committee looks into a report that the IRS spent excessively on conferences over the past several years.