The credibility of Robert Mueller's Russian collusion investigation of Donald Trump took two huge hits in the last 24 hours, as it is now an open question whether the FBI can conduct an unbiased probe into the allegations against the president.

First, it's been revealed that one of Mueller's chief investigators was fired for exchanging anti-Trump texts with a mistress who is a top lawyer in the bureau.  Peter Strzok, a former deputy director for counterintelligence at the FBI was removed earlier this year and now, the inspector general is looking into other "politically sensitive cases" that Strzok was involved in, including the Hillary Clinton email investigation. Strzok was also FBI liaison with the CIA.

Also, House Intelligence Committee chairman Devin Nunes  issued an angry letter to the FBI demanding to know why he and his committee were kept in the dark about the firing of Strzok. Taken together, the picture that emerges of the Mueller probe is one of a fatal anti-Trump bias that should disqualify Mueller - and the FBI - from carrying out what is supposed to be a non-partisan, independent, and unbiased investigation.

Byron York:

House Intelligence Committee chairman Devin Nunes has issued an angry demand to the FBI and Department of Justice to explain why they kept the committee in the dark over the reason Special Counsel Robert Mueller kicked a key supervising FBI agent off the Trump-Russia investigation.

Stories in both the Washington Post and New York Times on Saturday reported that Peter Strzok, who played a key role in the original FBI investigation into the Trump-Russia matter, and then a key role in Mueller's investigation, and who earlier had played an equally critical role in the FBI's Hillary Clinton email investigation, was reassigned out of the Mueller office because of anti-Trump texts he exchanged with a top FBI lawyer, Lisa Page, with whom Strzok was having an extramarital affair. Strzok was transferred to the FBI's human resources office — an obvious demotion -- in July.

The Post reported that Strzok and Page exchanged text messages that "expressed anti-Trump sentiments and other comments that appeared to favor Clinton."

Word of the messages and the affair were news to Nunes, even though the committee had issued a subpoena that covered information about Strzok's demotion more than three months ago. The committee's broadly worded subpoena for information related to the so-called Trump dossier went to the FBI and DOJ on Aug. 24. In follow-up conversations on the scope of the subpoena, committee staff told the FBI and DOJ that it included information on the circumstances of Strzok's reassignment.

On Oct. 11, Nunes met with deputy attorney general Rod Rosenstein. In that meeting, Nunes specifically discussed the committee's request for information about Strzok.

In an Oct. 31 committee staff meeting with the FBI, bureau officials refused a request for information about Strzok.

On Nov. 20, the committee again requested an interview with Strzok. (Three days earlier, on November 17, Strzok met with the Senate Intelligence Committee.)

On Nov. 29, Nunes again spoke to Rosenstein, and again discussed Strzok.

On Dec. 1, the committee again requested to speak with Strzok.

After each occasion, the FBI and DOJ did nothing. Now, in what appears to be an orchestrated leak, both the Post and Times published the reason for Strzok's demotion, along with concerns that the revelation might help President Trump. "Among federal law enforcement officials, there is great concern that exposure of the texts they exchanged may be used by the president and his defenders to attack the credibility of the Mueller probe and the FBI more broadly," the Post reported. 

Gee, ya think? Is there any further evidence needed for the partisan nature of this probe? In an independent, unbiased investigation, there should not be "great concern" that any information would be used by the "president and his defenders" to attack the credibility of Mueller's probe. What the hell should they care about the political defense being mounted by the president and his defenders? Why is that their concern? And is that any reason to defy congressional subpoenas?

Trump and his defenders don't have to "attack the credibility" of the probe. Mueller has handed them evidence of the politicization of the investigation all on his own. The credibility of the probe should. indeed be questioned when such jaw dropping information is withheld from relevant committee of congress - apparently for political reasons that include the fear that their biased, partisanship would be exposed.

Readers of this site know I am no fan of the president. But I am a big fan of the rule of law and fairness. This is an investigation that has been fatally compromised and to my mind, justifies either a massive overhaul of Mueller's operation or, failing that, his firing.

Any investigation that threatens to remove a president must be above partisan reproach - and this one fails to achieve that standard.