On Tuesday, Attorney General Jeff Sessions is scheduled to come before the Senate Intelligence Committee. His appearance represents Trump administration efforts to stem the political blood loss over the Russia scandal — Most notably, in the aftermath of former FBI Director James Comey's testimony last week.

But while the senators will ask many questions on Tuesday, there's one key question we need answering.

How many times in 2016 did Sessions meet with Russian Ambassador Sergei Kislyak?

In his open hearing testimony last week, Comey insinuated that there is more of a Sessions-Russia connection than previously outlined. Up until now, Sessions has insisted he only met with Kislyak twice in 2016. But following Comey's closed hearing with the intelligence committee, it was widely reported that Comey informed senators that Sessions met Kislyak three times last year.

The number of meetings matters for two key reasons.

First and most obviously, if Sessions did indeed meet Kislyak three times in 2016, why did he only admit two meetings? That omission was either deliberate or accidental. We need to know which, in order to know why. This also resurrects the question of why Sessions did not admit to meeting the Russian ambassador on his attorney general background investigation forms. The Department of Justice says Sessions was advised not to do so by the FBI investigator. But did Sessions tell that investigator he had three meetings with Kislyak or two?

Second, if there was a third meeting, we need to know what Kislyak and Sessions discussed.

The Russian ambassador has been openly outed by U.S. officials as the effective station chief of Russian SVR/GRU intelligence operations in the United States. Any off-the-books meetings with senior Trump campaign/administration officials are thus concerning. As I've noted before, Russia's intelligence-operation strategy is exceptionally aggressive. Even if Sessions discussed the weather at a third meeting, the Russians may have had other reasons for being there.

Ultimately, if a third meeting did indeed take place, it raises questions as to what Sessions was thinking. It strains the imagination to believe Sessions was unaware that the Russian ambassador is closely monitored by the FBI. That has been standard practice since the beginning of the Cold War. And again: When they did meet, what were Sessions and Kislyak talking about?

Perhaps Comey knows. Perhaps he doesn't. But Sessions definitely does. Now that Sessions is a member of the executive branch, so must we.