WASHINGTON - So, we know the U.S. intelligence community believes that Russia meddled in the presidential election to boost Donald Trump. We also know the FBI is investigating possible connections between Russia and some of Trump’s campaign allies.

What many Democrats - and even some Republicans - aren’t sure about is whether that investigation will live up to ethical standards. The man in charge of it, Attorney General Jeff Sessions, is one of Trump’s closest political allies, and a blockbuster report from The Washington Post asserts Sessions had two conversations with Russia’s ambassador in 2016, conversations he did not disclose during his confirmation hearings for the job.


‘‘I have not met with any Russians at any time to discuss any political campaign,’’ Sessions told NBC News in response to the report, adding: ‘‘I have said whenever it’s appropriate, I will recuse myself. There’s no doubt about that.’’

Some top Republicans are encouraging him to do just that, like Rep. Jason Chaffetz of Utah, chair of the Oversight and Government Reform Committee. ‘‘AG Sessions should clarify his testimony and recuse himself,’’ Chaffetz tweeted Thursday morning.

But what happens if Sessions steps aside? What kinds of investigations would take place instead? Here’s your cheat sheet to four major investigations that could delve into Trump’s relationship (or lack thereof) with Russia. We included pros and cons of each type of investigation, with our baseline being a fair and accurate one.

1) Various investigations by congressional committees.

The House and Senate intelligence committees, which deal with some of the nation’s most well-kept secrets, are already planning to investigate Russia’s attempt to influence the U.S. presidential election.

After Michael T. Flynn resigned earlier this month as national security adviser over his own conversations with Russia’s ambassador about sanctions, House Intelligence Committee Chairman Devin Nunes, R-Calif., said he’d consider expanding the panel’s investigation to Trump’s aides talking to Russia. He later added that he’s more focused on how reports of those conversations got leaked than he is on the conversations themselves.


GOP leaders of the House and Senate judiciary committees also have expressed a willingness to look into the circumstances surrounding Flynn’s conversations. GOP leaders haven’t immediately commented on this Sessions news, though Democrats certainly have:

Potential pros of this kind of investigation: It can begin right away.

Potential cons: It could be viewed by the public as partisan, since Republicans control both chambers of Congress and thus hold a majority in every committee that’s investigating Russia.

Likelihood of this kind of investigation happening: It’s very likely that Russia and Trump will be investigated in Congress in some form, although Republicans are divided about how seriously to take the allegations that Trump’s associates had contact with Russia.

2) A special congressional committee.

Under this scenario, a group of about a dozen lawmakers would be assigned to only investigate - well, whatever it was set up to investigate.

Potential pros: This kind of investigation is usually more thorough, because unlike other committees in Congress, it has only one issue to focus on. It also can be perceived as less partisan than the regular committee process, especially if Congress agrees to put an even number of Republicans and Democrats on it.

Potential cons: Most Republicans, including leaders, don’t seem to have any desire to set up a high-profile, time-consuming committee to investigate the issue. Even some of Trump’s toughest GOP critics, including Sen. John McCain of Arizona, have said it’s too soon to open a special congressional probe into who Trump’s aides talked to and when. (Though McCain has expressed support for a separate special committee to look into how Russia tried to influence the presidential election.)


Another con: This type of investigation could take years to get started and even longer to complete. And they are not immune to partisanship. Democrats and Republicans investigating the 2012 attacks in Benghazi, Libya, couldn’t even come to the same conclusion as to what actually happened when they released their final report in June.

Likelihood of it happening: Slim but not impossible. To get this committee started, a majority of lawmakers in one or both chambers must approve it, and there just doesn’t seem to be that kind of support.

3) The Justice Department expands its investigation.

The FBI, which sits under the Justice Department, is already investigating allegations of Russia hacking the U.S. election, including any financial ties between the Russian government and associates of Trump. It could expand that investigation however it feels necessary.

Potential pros: It’s lawyers, not Congress, (read: lawyers-turned-politicians) doing the investigating.

Potential cons: It’s largely being done behind closed doors and thus, it’s not really clear what, specifically, the FBI is investigating.

Also, the person ultimately in charge - Sessions - is a close ally of Trump’s. He was one of the first sitting members of Congress to endorse the president. That’s why Rep. Darrell Issa of California, a top Republican, recently said it may not be appropriate for Sessions to be in charge of the FBI’s investigation of Russia.


‘‘You’re right that you cannot have somebody - a friend of mine, Jeff Sessions - who was on the campaign and who is an appointee,’’ Issa said on a Friday show of HBO’s ‘‘Real Time With Bill Maher.’’ You’re going to need to use the special prosecutor’s statute and office.’’

Sen. Lindsey Graham, R-S.C., appeared to second that in a CNN town hall Wednesday:

‘‘There may be nothing there. But if there’s something there that the FBI believes is criminal in nature, then for sure you need a special prosecutor. If that day ever comes, I’ll be the first one to say it needs to be somebody other than Jeff.’’

Which brings us to the final kind of investigation being considered:

4) A special prosecutor.

A special prosecutor is someone - usually outside the confines of government - picked by the government to investigate potential wrongdoing.

The most famous special prosecutor in recent history is Kenneth Starr, a lawyer who was chosen to investigate President Bill Clinton’s real estate investments and eventually wound up uncovering the president’s affair with a White House intern.

Potential pros: It’s the most independent kind of investigation the government can have, because the government is not doing the investigating.

Potential cons: It can turn into a political spectacle in its own right - or uncover unexpected things. Starr’s broadened inquiry eventually led to Clinton’s impeachment by the House. And when Archibald Cox tried to force President Richard Nixon to turn over tape recordings of his White House conversations, Nixon fired the attorney general who appointed Cox.


Another con: Sessions could be the person to appoint the special prosecutor, which would for some critics lead us right back to the conflict-of-interest question haunting the existing investigations.

Likelihood of this happening: Slim, but not impossible. Even the White House isn’t ruling out a special prosecutor to look into Russian meddling in the election, although a spokeswoman said Sunday that it’s premature to say whether that’s necessary. Sessions told NBC News he’d consider it: ‘‘”I have said whenever it’s appropriate, I will recuse myself. There’s no doubt about that.’’