Republicans aren't satisfied with President Obama's explanation that he fired a controversial inspector general because he was "confused," "disoriented" and generally uncooperative. 

Rep. Darrell Issa, R-Calif., released a statement Thursday calling for a "fuller and more complete explanation" as well as more evidence of the "reasons and process" that led to the firing of Gerald Walpin, former inspector general for the Corporation for National and Community Service. 

"We see nothing that supports the administration's 'crazy old man' theory," said Issa, ranking Republican on the House Oversight and Government Reform Committee. 

Issa's office said White House lawyers met with investigators from his committee Wednesday but refused to answer specific questions about the dismissal -- the lawyers apparently described the firing as an act of "political courage." 

"While firing an investigator who uncovered the abuse of funds by a political ally might be considered an act of 'political courage' in Chicago politics, for most Americans it raises troubling questions," Issa said. 

Before his firing, Walpin had investigated Sacramento Mayor Kevin Johnson, an Obama supporter, for allegedly misusing federal funds. A settlement was reached in that case under which Johnson's organization was to repay some of the money. 

Walpin points to that investigation and others as the root of his dismissal, suggesting political motivations were behind it. 

The White House attempted to quell criticism that it did not initially provide a complete explanation for the firing with a letter Tuesday to key senators, explaining that Walpin, 77, was "confused" at a recent meeting, exhibited a "lack of candor" and "engaged in other troubling and inappropriate conduct." 

In an interview with FOXNews.com, Walpin called the White House explanation "insufficient" and "baseless." 

Sen. Charles Grassley, R-Iowa, who had originally raised questions about the firing, reportedly is not satisfied with the explanation either. 

And Republican Sens. Mike Enzi, R-Wyo., and Orrin Hatch, R-Utah, sent a letter Thursday to the White House requesting more information about the decision. 

But Democrats who had expressed concerns about Walpin's dismissal appear placated, for now. 

Sen. Claire McCaskill, D-Mo., released a statement Wednesday saying the president's reasons are "substantial" and the decision to remove Walpin "appears well-founded." She said the letter puts the White House in "full compliance" with the law, which requires the president to provide an explanation before firing an inspector general. 

Rep. Edolphus Towns, D-N.Y., chairman of the Oversight and Government Reform Committee, also had a different take than Issa on the briefing his panel received. 

He said in a statement Thursday that based on the information his panel learned in the briefing and his own review, "it appears that there was cause to remove Mr. Walpin based on misconduct." 

Towns added that, "due to the importance of preserving the independence of Inspectors General, I am continuing to review this matter." 

Meanwhile, Issa wrote a letter to Lawrence Brown, an acting U.S. attorney in California whose complaints about Walpin's conduct were among the reasons cited by the White House for Walpin's firing. Issa is asking Brown to provide additional information about the circumstances that led to the dismissal.