The unique feature of the House Select Committee on Benghazi is that its sole mission is to inflict political damage on a person who already has been exonerated by the collective force of seven congressional committees.

Update: Watch Hillary Clinton Benghazi hearing live stream.

The Benghazi committee was established by the House in May 2014 to investigate the terrorist assault that killed four Americans, including Ambassador Chris Stevens, in Benghazi, Libya. It was sold as an effort to find out what happened, whether the administration could have done more to prevent the attacks, and what could be done to protect US diplomatic facilities in the future. But the Benghazi inquisition is beginning to backfire on the Republicans because they really created it to hurt Hillary Clinton's chances of becoming the next president.

Last month, House Majority Leader Kevin McCarthy crippled the committee, and his own bid to become House speaker, by announcing on national television that its actions were bringing down Clinton's poll numbers. Since then, a fired staffer has accused the committee of dismissing him because he refused to target the Democratic presidential frontrunner, and a moderate House Republican from Clinton's adoptive home state of New York has said the committee was "designed" to hit her.

On Thursday, committee Republicans opened a made-for-television hearing with Clinton with three hours of questions that established no new facts, other than that Stevens didn't have her private email address. Clinton fielded their questions calmly, acknowledged that she was a force who pushed for the US to intervene in Libya in 2011 and disputed the notion that Sidney Blumenthal, a longtime confidant who did not work at State, was a top adviser to her.

The only real flare-up in the first part of the hearing was over whether Blumenthal's deposition, taken in June, should be made public. It was Democrats who argued for that, and Republicans voted down their motion.

None of it had anything to do with preventing future attacks or learning new information about the assault that killed Americans in Benghazi. The committee's modus operandi has been to focus on elements of the story unrelated to the attacks. Indeed, last Friday, Huma Abedin, the vice chair of Clinton's campaign and a former deputy chief of staff at State, testified before the committee behind closed doors. Clinton campaign spokesperson Nick Merrill said last Thursday night that Abedin, who is Clinton's closest personal aide, has no knowledge of Benghazi. He called the GOP's focus on her "just another tactic in their partisan plan to go after Hillary Clinton."

Clinton said Thursday that it was "deeply distressing" that she was being blamed for the death of Stevens, whom she regarded as a friend, and noted that US officials were not harangued after attacks that killed Americans during the Reagan and Clinton administrations.

It would be smart politically for Republicans to dissolve the panel before it helps Clinton and hurts them any more. But more important, the committee should be disbanded because it is a threat to the effectiveness of a very important congressional check on executive power. The viability of that tool, the select committee, should be preserved — even though it's being abused now.

When run properly, select committees are a vital tool for Congress

Throughout the history of the union, Congress has used select committees to investigate major national issues that are outside either the scope or the capacity of one of its existing committees.

The Senate Watergate Committee, the House and Senate select committees on the Iran/Contra affair, and the Senate Whitewater Committee are among the most famous in recent history. Joseph McCarthy infamously used the House Un-American Activities Committee and the Senate's Permanent Select Committee on Investigations, both of which functioned like select committees, to target suspected communists in civilian government, Hollywood, and — leading to his eventual undoing — the Army. While they aren't always investigative in nature — House Democrats had a select committee on climate change for a while — the most prominent and consequential generally are.

They also tend to have a naturally partisan tilt. A House or Senate controlled by Democrats is less likely to appoint a select committee to investigate a Democratic president, and the same is true for Republican-run chambers when a Republican is in the White House. Because the president has power over the Justice Department and the FBI — the ability, in some cases, to prevent probing — it's a good thing that Congress has the authority to conduct its own special investigations.

So it's taken as a given in Washington that select committees are usually established with a dual purpose in mind: that they will uncover wrongdoing — usually by the administration of the other party's president — and that the wrongdoing will hurt the president and his party politically.

The key, though, is that there are actual substantive misdeeds that can be revealed to the public, which puts pressure on federal investigators and prosecutors to bring charges against the president or members of his administration — or at the very least force the administration to make changes that improve governance.

But in Clinton's case, no one in a position of authority has made a plausible argument that she was guilty of malfeasance or serious negligence. There was no reason for House Republicans to think that the select committee would turn up anything related to the Benghazi attacks that hadn't been exhumed already by Congress.

The Benghazi committee's work is at odds with its purpose

On the surface, the Benghazi committee was established to look into some important matters.

What, if anything, the administration could have done to prevent the assault on US facilities in Benghazi, Libya, in September 2012 Whether the administration responded appropriately to the attacks Whether anyone in the administration acted in an improper or criminal way in relation to the attacks How the executive branch can limit the risk of another similar tragedy

In practice, it has done none of those things — primarily because several other congressional committees and a State Department review board already investigated them. Seven existing congressional committees conducted investigations into aspects of the Benghazi attacks before the select committee was created, and not one of them concluded that Clinton was guilty of any wrongdoing.

But that wasn't good enough for House Republicans, who were under immense pressure from constituents and talk radio hosts to keep the spotlight on Clinton. So they formed a select committee in May 2014, with the help of a handful of Democrats facing reelection in tough districts who had reason to fear that they would look like they were covering up if they voted against another investigation.

With nothing of substance left to look into, the Benghazi committee, run by former prosecutor Trey Gowdy, has spent about 17 months obtaining documents that later leaked into public view. They are almost exclusively related to Clinton's use of a private email server during her time at the State Department. And they surely would have come out anyway as a result of a series of federal lawsuits — some launched by political groups obsessed with destroying Clinton — aimed at forcing the State Department to comply with Freedom of Information Act requests.

If the purpose was to find out what happened and prevent it from happening again, the committee frustrated its goal by becoming so partisan and so focused on one person.

One thing we can all be entirely certain of is that Hillary Clinton's email didn't attack the US diplomatic and intelligence compounds in Benghazi. And anyone who thinks Clinton ordered, encouraged, or condoned the murders of these Americans is living in a very dark and twisted fantasy world.

For the good of Congress, kill the Benghazi committee and keep select committees alive

Congress needs the select committee option to focus attention on grievous wrongdoing by a president or his/her administration. It has proven, at times, to be a very effective truth serum for powerful officials in the past.

The Senate Watergate Committee's revelations included testimony from White House Counsel John Dean that President Richard Nixon was directly involved in the cover-up after a break-in at the Democratic National Committee's headquarters in Washington's Watergate building.

But the continued operation of the Benghazi committee's three-ring, $4.6 million circus risks making that tool less effective in the future. It simply wasn't designed to investigate things that never happened — like Clinton bearing primary responsibility for the Benghazi attacks. Select committees can have a partisan edge, but they shouldn't be solely about partisan politics. They should be directed toward solving mysteries for the American public.

There's no mystery here: Hillary Clinton isn't to blame for the Benghazi attacks.