Senate Majority Leader Mitch McConnell (R-Ky.) sent an unsubtle message Tuesday when, during a speech from the Senate floor, he declared that the investigation of connections between Donald Trump’s 2016 presidential campaign and Russia was a “case closed” situation. McConnell’s argument was intentionally broad, seeking to stamp a wide range of issues not conclusively settled by special counsel Robert S. Mueller III’s investigation as having been cleared by the inquiry.

At least one member of his caucus, Sen. Rand Paul (Ky.), understood the message.

“Apparently the Republican chair of the Senate Intel Committee didn’t get the memo from the Majority Leader that this case was closed,” Paul tweeted Wednesday evening. He was referring to Sen. Richard Burr (N.C.), chairman of the Senate Intelligence Committee, which, that day, had subpoenaed the president’s son Donald Trump Jr. to answer more questions about the events of the campaign and his involvement with them.

Trump Jr. is a very good example of how the case isn’t closed — at least not entirely. He has testified before the Intelligence Committee already, in December 2017, an appearance that came a few months after he spoke with the Senate Judiciary Committee in September. Over the course of that latter testimony, which was later made public, Trump Jr. claimed at least 54 times that he couldn’t remember details of the subjects of the questions. It was a performance that mirrored his father’s answers to questions posed by the special counsel, when Trump claimed not to recall answers far more often than he offered any.

It has been more than a year since the Intelligence Committee interviewed Trump Jr., a year during which we’ve learned substantially more about what he was doing during the campaign. We have, for example, seen most of Mueller’s report detailing the conclusions of his team’s investigation.

There are three components of Mueller’s inquiry in which Trump Jr. plays a significant role. There’s his exchange with WikiLeaks through direct messages on Twitter. There’s his involvement in the proposed development of a tower in Moscow. And, of course, there are the events that led to his meeting with a Kremlin-linked lawyer at Trump Tower on June 9, 2016.

This would seem to be one of those “case closed” situations in McConnell’s estimation. After all, Mueller’s report determined that no illegal activity occurred; specifically, that there wasn’t sufficient evidence of a violation of campaign finance rules to be able to prosecute Trump Jr. or others involved.

But there are still many unanswered questions about the meeting that speak directly to the question of how willing the campaign was to partner with Russian nationals and, more broadly, the Russian government.

You’ll recall that the genesis of the meeting was an email sent to Trump Jr. from a music promoter named Rob Goldstone. The first message from Goldstone proposed a meeting predicated on two specific things: It involved information that was harmful to Democratic nominee Hillary Clinton, and it came as part of the Russian government’s support for Trump. Goldstone has subsequently waved away this description as being hyperbole intended to entice Trump Jr. (which, if that’s true, worked like a charm).

The initial email from Rob Goldstone, referencing his employer, Emin Agalarov, and Agalarov's father, the developer Aras Agalarov. (Donald Trump Jr./Twitter)

It seems likely that there was external pressure from the Russian government to make a connection with Trump’s team.

The actual subject of the meeting, according to those who attended, was a law called the Magnitsky Act, which sanctioned prominent Russians for the death of an anti-corruption activist in a Russian prison. In response to the passage of the law during the Obama administration, Russian President Vladimir Putin blocked Americans from adopting Russian children. (This is why adoptions would have been raised during the Trump Tower meeting — and why that was the rationale for the meeting Trump Jr. later offered the news media.)

Why this law would be of concern to real estate developer Aras Agalarov and his son Emin Agalarov — whose side career as a pop star led him to hire Goldstone — isn’t clear. The Agalarovs were not a target of the sanctions. But they had met Trump in 2013 when Donald Trump brought the Miss Universe pageant to Moscow, so it was well known that the Agalarovs had a connection to the Trump family. (Putin was aware of the 2013 event, as Trump invited him to attend.) Mueller’s report indicates that on two occasions after the election, Aras Agalarov’s team tried to set up meetings with Trump or his staff to revisit the subject. (See Volume I, p. 120.)

If Agalarov’s interest isn’t clear, Putin’s is. Trump says that when he and Putin met in Europe in July 2017, right before news of the Trump Tower meeting broke, they discussed the subject of adoptions. When the two met in Finland in July, Putin raised the Magnitsky Act explicitly during a joint news conference.

As The Washington Post reported in July 2017, Agalarov’s work as a developer brought him close to Putin’s government.

“A series of important government infrastructure projects, including a $1.2 billion university campus in Russia’s Far East and stadiums for the upcoming World Cup,” Andrew Roth wrote then, “have made [Agalarov] a trusted executor for the Kremlin, if not a member of Russian President Vladimir Putin’s inner circle.”

It doesn’t particularly strain logic to think that perhaps Agalarov was asked to connect Trump with Natalia Veselnitskaya, a lawyer who attended the meeting. Although she initially denied any connections to the government, she eventually admitted that she’d worked with prosecutor general Yury Chaika — the person many people think Goldstone was referring to in his initial email when he referenced a meeting between Agalarov and “the Crown prosecutor."

The question, then, is whether Trump Jr. and Trump knew or believed that this connection to Putin existed.

The conduit to Trump Jr. for that information would have been Emin Agalarov, who worked with Goldstone to set up the Trump Tower meeting. At the time he testified before the Senate committees, Trump Jr. claimed that he didn’t remember whether phone calls between himself and Agalarov resulted in any conversation. He said they had perhaps exchanged only voice mails.

In an interview with Vice News last year, though, Emin Agalarov was more certain: The two had spoken.

“I said, ‘Listen, there’s some people that want to meet you,’ ” Agalarov told Vice about the conversations which included three calls. “'They obviously want something that could potentially help them resolve things that you could be interested in or maybe not. If you can spare a few minutes of your time, I’d be grateful. If not, no problem.' Obviously Don Jr. obviously being Don Jr. said, ‘Of course. I’ll do it if you’re asking.’ ”

There's not a lot of value to Agalarov in implicating the Trumps. But that he claims they did speak, something Trump Jr. denied, is certainly worth exploring.

Then there’s the broader question of what Trump knew and when. In his written testimony for Mueller, Trump said he didn’t remember whether he knew about the meeting in advance. In attendance at the meeting were several key members of his campaign team: Trump Jr., campaign chairman Paul Manafort and his son-in-law, Jared Kushner.

“I have no recollection of learning at the time that Donald Trump, Jr., Paul Manafort, or Jared Kushner was considering participating in a meeting in June 2016 concerning potentially negative information about Hillary Clinton,” Trump’s response to Mueller reads. “Nor do I recall learning during the campaign that the June 9, 2016 meeting had taken place, that the referenced emails existed. or that Donald J. Trump, Jr., had other communications with Emin Agalarov or Robert Goldstone between June 3, 2016 and June 9, 2016.”

His answers to Mueller conceded that his calendar indicated that he had a meeting with Manafort the morning of the meeting but that he “[did] not recall if that meeting took place. It was more than two years ago, at a time when I had many calls and interactions daily.”

The Senate Judiciary Committee asked Trump Jr. whether Manafort discussed the meeting with Trump when he saw him, and he said he didn’t know. But then, Trump Jr. also said he didn’t remember calling Manafort shortly before finalizing the time of the meeting in an email to Goldstone on June 7.

Trump Jr. declined to speak with Mueller's investigators. Why he wasn't subpoenaed for his testimony isn't clear.

Michael Cohen, a former personal lawyer for Trump, alleged during sworn testimony on Capitol Hill earlier this year that he was in Trump’s office when Trump Jr. came in to inform the candidate that “the meeting is all set.” What meeting was set wasn’t clear but Cohen claimed that the incident happened in early June 2016.

There’s reason to suspect that Trump did know. During a speech he gave on the evening of June 7, he claimed that he would be giving “a major speech on probably Monday of next week, and we’re going to be discussing all of the things that have taken place with the Clintons.” He made a promise to reporters: “I think you’re going to find it very informative and very, very interesting.”

During his testimony before the Senate Judiciary Committee, Trump Jr. was asked about that speech. Was it a coincidence, for example, that Trump said the information would be “very, very interesting” when Goldstone’s initial email also described the offered information as “very interesting”? It was a coincidence, Trump Jr. said, and “that’s the way my father speaks.”

He also said that, although he didn’t know what Trump was referring to, it probably dealt with information from the book “Clinton Cash.” The book had been released more than a year earlier and was already public.

It obviously would be interesting to determine the extent to which Trump Jr. believed he was getting information from the Russian government and whether he passed that on to his father. Not necessarily because it meets some heretofore unmet standard of conspiracy but, instead, because it would speak more broadly to the Trump team’s willingness to work with Russia directly. Because it could shed light on the extent to which Trump was being honest about what happened during the campaign, given that, when not under oath, he has explicitly denied having known about the meeting.

It’s the sort of thing that’s worth determining as conclusively as possible. Put another way, a lot of questions remain open.