Republicans from President Trump down often declare that there was no collusion between Russia and the Trump campaign during the 2016 election. So far, Democrats have not been able to prove otherwise. But the most compelling piece of evidence cited by the president's opponents is the June 9, 2016, meeting in Trump Tower between Donald Trump Jr., some key Trump campaign aides, and a group of Russians who came promising damaging information about Hillary Clinton. Much remains unknown about that meeting.

A pre-meeting email from, improbably, a British music promoter, Rob Goldstone, to Trump Jr. was almost of a parody of a "WE WOULD LIKE TO COLLUDE WITH YOU" invitation. A powerful Russian had "offered to provide the Trump campaign with some official documents and information that would incriminate Hillary and her dealings with Russia and would be very useful to your father," Goldstone wrote Trump Jr. "This is obviously very high level and sensitive information but is part of Russia and its government's support for Mr. Trump …"

"Seems we have some time and if it's what you say I love it," Trump Jr. replied.

The meeting apparently came to nothing, when it became clear after a few minutes that the Russian lawyer at the center of it, Natalia Veselnitskaya, had no information about Clinton and instead wanted to lobby for an end to U.S. Magnitsky Act sanctions against Russia. And then the whole affair took a turn toward the fishy when it was learned that Glenn Simpson, the opposition researcher whose firm, Fusion GPS, commissioned the Trump dossier, met with Veselnitskaya both before and after the Trump Tower meeting. What was going on?

The potential importance of the June 9 meeting makes it enormously important for the public to learn as much as possible about what led up to the meeting, what happened during the meeting, and what happened after. Yet we've heard very few details, and certainly not from official sources, about those events.

Special counsel Robert Mueller presumably knows a lot about the meeting, but he's not talking. The House and Senate Intelligence committees have interviewed several meeting participants, but the transcripts of those interviews remain under wraps.

Now, things might be about to change. The Senate Judiciary Committee has also interviewed several of the players in the meeting, and the chairman, Republican Sen. Chuck Grassley, R-Iowa, says he wants to release the transcripts. But first, he has to get committee Democrats to go along.

The Judiciary Committee has interviewed Trump Jr. It has received written answers to questions from Veselnitskaya. It has interviewed Goldstone. It has interviewed the Russian-American lobbyist Rinat Akhmetshin. It has interviewed the Georgian-American businessman Irakle Kaveladze. And the translator at the meeting, Anatoli Samochornov.

The Judiciary Committee has not interviewed Jared Kushner or Paul Manafort, the other high-ranking Trump campaign officials at the meeting. Manafort, facing indictment, is out of the game, but Grassley had hoped to interview Kushner. That hope seems gone after a late January Judiciary Committee meeting in which Grassley said he believed the decision by the committee's ranking Democrat, Sen. Dianne Feinstein of California, to unilaterally release the transcript of the committee's interview of Simpson had "spooked other potential witnesses."

"As a result, it looks like our chances of getting a voluntary interview with Mr. Kushner have been shot," Grassley said. "He has already provided his account to the Intelligence Committee."

Therefore, Grassley concluded, "I believe this committee's interviews of the witnesses surrounding the Trump Tower meeting are complete. That section of our investigation is done. So, now it's time to start officially releasing the transcripts of all witness interviews we have done related to that meeting." The chairman said he'd like to see the transcripts made public "as soon as possible."

Grassley said that on Jan. 25. March is here, and the transcripts have not yet been released. Word is the committee is dealing with some Democratic delays, as well as with issues with some witnesses who are entitled to look over the transcripts of their interviews before release.

What could the transcripts tell the public?

First, one thing they will not tell. The emails setting up the meeting are what they are, and having multiple accounts of what happened in the meeting will not change the baiting nature of the Goldstone email or the take-the-bait nature of the Trump Jr. response.

But it would be important to see the various accounts of what happened before, during, and after the meeting. We've had a number of stories to the effect that Veselnitskaya had nothing to offer the Trump team and instead went straight into a pitch for ending the Magnitsky Act, which instantly turned off the Trump people, who soon began trickling out. First-person recollections of what happened would be valuable.

It would also be worthwhile to read the testimony of Samochornov, the translator who presumably did not have a lot at stake in the meeting. How did he assess what was going on?

And it would be useful to see if the transcripts shed any light on the Simpson question. Simpson had dinner with the meeting participants just hours later on June 9, 2016, but testified that no one brought up the Trump Tower meeting at all. "I was not aware of the Trump Tower meeting, and no one told me about it before it, and no one told me about it after," Simpson told the House Intelligence Committee last November. The transcripts might shed additional light on that.

Grassley's plan is to give the public the whole group of transcripts at once to avoid the piecemeal interpretation that has characterized much of the Trump-Russia investigation. "Our intention is to release all of the transcripts at the same time to provide the public with the fullest view of what we've learned about the June 9 meeting," said Judiciary Committee spokesman Taylor Foy.

In any event, it's just a good thing for the public to know more, rather than less, about the Trump-Russia affair. Too much material is secret, too much is classified, and too many attacks are launched and defenses mounted with too little public knowledge of the underlying facts.

Here's hoping Grassley can convince his fellow committee members to release the transcripts soon.