The political bias mentioned in the Intelligence Community Inspector General report refers to the fact that the anonymous whistleblower who filed a complaint about President Donald Trump's interactions with the Ukrainian President is a registered Democrat, a source familiar with the ongoing investigation told CNN Thursday.
The intelligence community's inspector general, Michael Atkinson, acknowledged an indication of possible political bias in his assessment of the complaint but made clear that it did not change his overall conclusion that it appeared to be credible.
"Further although the ICIG's preliminary reviewed identified some indicia of bias of an arguable political bias on the part of the complainant in favor of a rival political candidate, such evidence did not change my determination that the complaint relating to the urgent concern 'appears credible' particularly given the other information the ICIG obtained during its preliminary review," Atkinson wrote.
The attorney for the whistleblower would not confirm nor deny his client's political affiliation.
An expert on whistleblowers tells CNN he suspects the inspector general included the "possible bias" language, before dismissing it, as "a CYA measure" since being of the other party -- a party the President once belonged to -- is not disqualifying in any way.
Despite Atkinson and acting Director of National Intelligence Joseph Maguire saying they believed the whistleblower acted in good faith, Trump and some of his Republican allies have sought to discredit the individual.
Maguire broke with Trump and his Republican supporters last week during an open hearing on Capitol Hill, defending the whistleblower and the intelligence committee watchdog who exposed contacts with Ukraine that could help lead to the President's impeachment.
"I believe that the whistleblower and the inspector general have acted in good faith throughout. I have every reason to believe that they have done everything by the book and followed the law," Maguire said while testifying before a key House committee.
But the partisan attacks have only intensified as Democrats began interviewing witnesses named in the complaint, which was released last week along with a rough transcript of the President's July 25 call with the Ukrainian leader, made public by the White House.
Despite claims to the contrary by Trump and his defenders, both the transcript and complaint show the President repeatedly pressed his counterpart to investigate former Vice President Joe Biden and his son. There is no evidence of wrongdoing by either Joe or Hunter Biden.
Yet, Trump and Republicans have also claimed, without evidence, that the whistleblower is a partisan actor and attempted to undercut the individual's credibility with a series of baseless allegations related to how the complaint was handled.
On Thursday, Trump repeated his criticism of a whistleblower complaint, saying it was "total fiction" and repeating his conversation with Ukraine's President was "absolutely perfect."
On Wednesday, Reuters' Jeff Mason had asked Trump the same questions, which is at the center of the impeachment storm. What did he want from Ukraine's President if it was not, as it appears from a transcript of their July 25 telephone call, dirt on his potential 2020 election rival?
When Mason, repeatedly but respectfully tried to follow up, Trump snapped: "Ask this gentleman a question. Don't be rude."
"I've answered everything. It's a whole hoax, and you know who's playing into the hoax? People like you and the fake news media that we have in this country," the President added.
But on Thursday, Trump laid out exactly what he wanted -- investigations of a potential political rival by Ukraine and China.
Trump says he hasn't yet asked his Chinese counterpart to investigate Joe Biden and his son.
But he said it was something he'd consider, alleging the Bidens engaged in wrongdoing.
"I haven't but clearly it's something we should start thinking about," he said when asked whether he'd raised the matter with China's Xi Jinping.
CNN's Zachary Cohen contributed to this report.