Updated at 12:31 p.m. ET

One of the biggest disputes in the Brett Kavanaugh saga has not been over what questions should be asked about the alleged sexual misconduct of which he's been accused and which he strongly denies — but who asks them.

Specifically, Democrats and outside groups want the FBI to conduct an investigation into the accusations made by Christine Blasey Ford and others about the Supreme Court nominee's conduct from decades ago. Democrats repeated this demand at a dramatic hearing on Thursday, during which both Ford and Kavanaugh testified before the committee. An outside prosecutor assisted senators with the questioning.

But Senate Judiciary Committee Chairman Chuck Grassley, R-Iowa, and Kavanaugh himself both say the committee is what's important here. Its members and staff are the ones who must draw conclusions about what they believe so its members can vote on whether to recommend his nomination to the full Senate.

The FBI, as Grassley and Kavanaugh pointed out in Thursday's hearing, wouldn't make any independent findings about the substance of the claims. Its investigators likely would simply conduct interviews with the people involved and then pass them along.

If that's so, why is the role of the FBI still such a big deal even after the historic, emotional marathon of open testimony?

The weight of the FBI

There are several reasons why an FBI investigation would be different. First, because it's a crime to lie to the FBI. It's a crime to lie to Congress too, but there is a practical difference between people in the Kavanaugh case issuing written statements about their versions of events and actually sitting down with human FBI special agents.

And second, because the FBI might hear from, and ask questions of, people who so far have only spoken out on paper. Special agents might talk in more detail with bystanders and witnesses and glean details from them that aren't yet in the public eye.

So although Grassley and Kavanaugh are correct that the FBI might only serve as a gold-plated transcription service in this case, the completeness of those transcripts might exceed the body of evidence that now exists — and it would be evidence obtained from witnesses who could be prosecuted if they lied to the feds.

That leads to the third important point in all the discussion about an FBI investigation: Democrats and outside groups want whatever the Judiciary Committee or the Senate considers to have the imprimatur of the world's premier law enforcement agency.

An interview given to the FBI by Kavanaugh's boyhood friend Mark Judge, for example — whom Ford has accused of being a bystander to sexual assault — would have much greater political heft than the written statement he has released on his own.

On Friday, the committee voted along party lines to defeat a Democratic motion to attempt to subpoena Judge to testify before the panel.

The case made by Democrats and outside groups goes beyond Judge. They also want interviews with other accusers and witnesses in the case, some of whom have already said they want to talk with investigators.

What about Senate investigators and Kavanaugh's background checks?

Republicans say the call for an FBI investigation is a transparent bid to continue delaying Kavanaugh's nomination. The Senate already has been reviewing his case for weeks.

There's no way to know how much more time it might require for the FBI to interview all the people now involved with the Kavanaugh case. Some of them are spread around the country.

Moreover, Grassley has said, the Judiciary Committee also already has federal investigators detailed to help it talk with people involved — they just come from the Bureau of Alcohol, Tobacco, Firearms and Explosives and U.S. Immigration and Customs Enforcement.

These ATF and ICE investigators, however, so far apparently haven't spoken to Judge or other people directly connected with the allegations made by Ford and the other women.

The committee's staffers and investigators have been dealing with other allegations, according to transcripts released by the Judiciary panel, including ones they and Kavanaugh have concluded were false.

And the FBI has conducted background checks into Kavanaugh in the past, as he and Judiciary Committee Republicans pointed out several times on Thursday.

If the bureau didn't find anything that disqualified him for his executive branch positions or his current seat on the D.C. Circuit Court of Appeals, what difference, they ask, would a new inquiry make?

One difference is what the people involved are willing to say now.

Ford says she didn't talk with anyone about her alleged assault at the time it happened in 1982, including in the 1990s at the time the FBI might have looked into Kavanaugh's background so he could join the Justice Department, or in the early 2000s when he worked for then-President George W. Bush.

What Democrats and some outside groups want is to see what the FBI might come up with if it looked into Kavanaugh today, with everything that has happened in the past month.

That does not appear likely.

President Trump has declined the request of Democrats to order another FBI investigation. Kavanaugh has said he will not ask the White House to request one, and Grassley argues that one isn't necessary.

What Republicans say is the due diligence on Kavanaugh is complete and now it's time for the Judiciary Committee to vote on whether to recommend him to the full Senate — and then for the chamber itself to decide.

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