I’ve spent a good part of my day sitting in my study. My TV has been tuned to a cable news channel, which has been broadcasting a congressional hearing with a single witness: FBI agent Peter Strzok.

My question is this: For what purpose are they conducting this all-day marathon?

Strzok used to serve on Robert Mueller’s team that is looking at Donald Trump’s presidential campaign. Then he and another agent, Lisa Page, were fired. Mueller canned them when it became known that they had exchanged anti-Trump messages via e-mail. Congressional Republicans allege a deep bias against the president. They are contending that the alleged bias taints the Mueller probe. They are seeking to undermine Mueller’s probe.

So, where is this investigation going? The U.S. House Oversight Committee is going to issue some kind of report. Then what? Suppose the report determines Mueller’s team has been biased and has conducted a corrupt investigation into whether the Trump campaign “colluded” with Russians who meddled in our 2016 election. Are they going to recommend an end to the probe?

Strzok has defended himself fiercely. He said he and the FBI did everything “by the book.”

I keep circling back to the man at the top of the investigation, Robert Mueller.

I remain quite convinced that Mueller’s integrity is intact. He is a former FBI director. He is known to be a meticulous lawyer. Mueller has assembled a top-tier legal team to probe deeply into the myriad issues surrounding the Trump campaign.

As for the president’s assertion — backed up by his GOP allies in Congress — that the Russia probe is being dominated by “13 Democrats,” this flies in the face of the fact that Mueller is a life-long Republican; so is the man who appointed him, Deputy Attorney General Rod Rosenstein; and … so is the man Trump fired as FBI director, James Comey.

Trump accuses Mueller of launching a “witch hunt” against him. I strongly suspect another type of “witch hunt” is under way. It ‘s occurring in Congress and the target is Mueller, who the GOP is targeting because he is inching closer to the White House in his probe into what happened during the 2016 presidential campaign.

House Oversight Committee Republicans have one of Mueller’s former team members — Peter Strzok — in their sights.

Where in the world is this congressional probe heading? I think it will end up in the ditch, right along with the Benghazi probe.