(CNN) -

Rick Perry's lawyers pushed back against a central accusation by Democrats that the Texas governor's office was being investigated about questionable funding for a cancer research project.

The accusations over the Cancer Prevention and Research Institute of Texas, CPRIT, are tangential to the two felony charges against the longtime Republican governor over his veto of funding for the Public Integrity Unit. His lawyers Thursday called the cancer funding accusations a "red herring."

His lawyers released an affidavit from a former criminal investigator with the PIU to dispel any notion that Perry's veto was related to cancer research funding. In the affidavit, Chris Walling said he was not investigating anyone in the governor's office "during or after" the veto of PIU funding.

"Any suggestion that Governor Rick Perry or anyone associated with him was being investigated is untrue," Walling wrote.

The Texas Democratic Party has been honing in on cancer research funding as a reason Perry -- who's considered a potential 2016 GOP presidential candidate -- vetoed PIU funding.

"It's no coincidence that Perry tried to eliminate the PIU while they were investigating the Cancer Research Institute -- a state institution that gave more than $40 million in taxpayer funds to Abbott and Perry donors," Texas Democratic Party Executive Director Will Hailer said in a recent statement. Greg Abbott is currently running for governor.

Ed Espinoza, head of the liberal group "Progress Texas," was dismissive of the claim made in Walling's affidavit.

"Does Rick Perry's high-priced legal team really expect us to believe that the governor had no interest in protecting his signature project?" Espinoza asked in a statement released Thursday. "This was a scandal-plagued agency that has already seen one of its officers receive a felony indictment for funneling millions to donors of Rick Perry and Greg Abbott."

The case centers on Perry's June 2013 veto of the $7.5 million budget for the unit run by Rosemary Lehmberg, after she refused his demand to resign following her drunken driving arrest and conviction.

Perry addressed the indictment during an event in Washington, D.C. Thursday, saying he is "very confident" that he will be cleared of any wrong doing.

"These are fundamentally principles that are very important, namely a governor's power to veto legislation and funding and the right of free speech," he said at an event hosted by the conservative Heritage Foundation.

At the time of Perry's veto, an investigation of CPRIT was taking place, however, leading to the indictment of one executive of the program.

"At no time in CPRIT investigation was Governor Rick Perry or anyone from the governor's office a target," Walling wrote.

Perry's attorney, Ben Ginsberg, who also represented President George W. Bush during the 2000 recount, told reporters that "Democrats are trying to make it float up stream," insisting that Perry's indictment falls apart with the release of this affidavit.