A relatively small group of people specialize in this type of work and their names come up, depending on their age, across some the biggest Washington controversies from Watergate on.
The list of potential witnesses in such politically perilous investigations can be long, and even witnesses with little direct involvement are likely to need lawyers to shepherd them through interactions with the authorities. Caldwell Butler, who helped draft the impeachment articles for President Richard Nixon.
Pence's office announced on June 15 the decision to hire Richard Cullen, the chairman of McGuireWoods LLP law firm. Paul Trible, R-Va., in the Iran-contra investigations. And although they did not overlap, both served in the USA attorney's Office in Richmond.
The relationship is personal: Cullen is godfather to one of Comey's daughters, according to the Post. He served as special counsel to former Sen.
In 2007, Cullen was one of 26 business and civic leaders in the Richmond area who signed a letter calling for fundamental changes in Richmond's school system, including a return to appointing School Board members, instead of electing them.
The new allegations against Trump centre on his own admission that he fired Comey because of the Russian Federation investigation, and suggestions he asked several top intelligence officials for their help altering the direction of the inquiry.
Regardless of the outcome, the spectre of Mueller examining the possibility of obstruction of justice appeared to be a new blow to Trump, whose first five months in office have been clouded by the federal and congressional probes into the Russian Federation issue.
In fact, Pence's decision to hire outside counsel has precedent.
"It's very routine", Pence said.
Since there is no way to find traces of a "collusion" between the Trump environment and Russia, the democratic opposition and the United States media close to it have recently begun to assert that the president and his aides tried to cover up traces of contacts with Russians and thereby prevented the administration of justice.
Mark Corallo, a spokesman for the outside counsel, did not respond to an email and phone call seeking comment on the questions Sanders referred to him.style="text-align: center;"