All over Washington, politicians are calling for independent investigations into Russian interference in the election. But not everyone is calling for the same thing. Here’s a quick guide to what people generally mean when they call for different kinds of “independent investigations.”

SPECIAL COUNSEL

The Justice Department can appoint a special counsel, also often called a special prosecutor, any time the person who would ordinarily handle a matter is believed to face a conflict or might be perceived to hold potential bias.

Attorney General Jeff Sessions has recused himself from involvement in probing the Russia matter, so it is up to Deputy Attorney General Rod Rosenstein to decide whether to appoint a special prosecutor.

Congress does not have the power to appoint a special counsel, though some Democrats have been publicly urging Rosenstein to do so.

Once appointed, a special counsel would work with the FBI and the court system to subpoena documents, conduct interviews and potentially seek criminal charges.

During Watergate, Attorney General Elliot Richardson appointed Archibald Cox to serve as a special counsel investigating the White House’s actions with regard to the break-in at the offices of the Democratic National Committee. The Senate had made the appointment a condition of confirming Richardson. Back then, there were few rules that governed the set-up. The special counsel had no true independence – he could be dismissed by the attorney general or president. Indeed, President Richard Nixon ordered that Cox be fired in the 1973 Saturday Night Massacre.

These days, there are formal Justice Department rules that govern how special prosecutors operate, intended to provide more independence. But one thing has not changed: Any president willing to face the political consequences still has the authority to dismiss a special counsel.

INDEPENDENT COUNSEL

A law creating a process for appointing an independent counsel, or independent prosecutor, was passed after Watergate but allowed to expire in 1999 amid displeasure over independent investigations of President Bill Clinton.

Under the 1978 statute, the attorney general started the process while the appointment of an independent counsel was formally made by a panel of federal judges from the U.S. Court of Appeals for the District of Columbia Circuit. The judges would then oversee the independent counsel’s work. Under the statute, the independent counsel could be dismissed only for “good cause.”

Under current law, however, there is no mechanism to appoint an independent counsel or prosecutor. Congress could, in theory, pass a law establishing an independent counsel, either creating a process for naming independent counsels generally or specifically appointing a prosecutor to look into the Russia matter. It seems unlikely that Congress would do so, given that the legislation would require support from the Republican-led House and Senate, as well as President Trump’s signature.

Special or select congressional committee

Congress has broad power to investigate matters of public concern. Congressional panels can issue subpoenas for documents or testimony from relevant witnesses and issue reports with their findings or even initiate impeachment of public officials. Congressional committees do not, however, have the ability to seek criminal charges.

Currently, both the House and Senate Select Committees on Intelligence are probing the Russia matter.

SPECIAL COMMISSION

Another option would be for Congress to appoint a special congressional committee composed of members of the House or Senate who have been appointed specifically to examine the issue. Typically, select committees are formed by a resolution adopted by a vote of the chamber establishing the committee.

A special committee could bring more focused attention to the issue, but there is no guarantee it would be free from partisanship. For instance, the special House committee that probed the attacks on the U.S. installations in Benghazi, Libya, was marked by bitter clashes between the Republican majority and their Democratic counterparts.

Another option for Congress would be to establish an independent commission, composed of members who do not serve in Congress. Congress would be free to establish the rules for the commission, includes qualifications to serve.

Creating a commission requires passage of a law signed by the president.

Congress in 2002, for instance, established a special commission to investigate the Sept. 11, 2001, terrorist attacks, requiring that its membership include five Democrats and five Republicans. That panel held high-profile hearings with testimony from top officials and published one of the most comprehensive accounts of the attacks and the government’s response.

Congress can agree to give a commission certain powers, including subpoena power, but a congressionally appointed commission cannot seek criminal charges.