Here's who's in the running to replace Preet Bharara, the 'Sheriff of Wall Street'

AP Photo/Evan Vucci

United States Attorney General for the Southern District of New York Preet Bharara speaks with reporters at Trump Tower, Wednesday, Nov. 30, 2016, in New York.

President Trump created waves when he fired Preet Bharara, US attorney for the Southern District of New York, over the weekend.

While it's customary for presidents to replace the previous administration's political appointees - which US attorneys are - Bharara's firing came as a surprise to many, because Trump had asked him to stay on when they initially spoke.

The timing of Bharara's dismissal was also characterized as somewhat abrupt, because the Trump administration had not yet named a replacement for him.

While the president has still not nominated Bharara's successor, two frontrunners have emerged.

Marc L. Mukasey

Marc Mukasey currently serves as the Global Co-Chair of Greenberg Traurig's White-Collar Defense and Special Investigations Practice. He has experience working as a former prosecutor for New York's Southern District, and he is the son of Michael B. Mukasey, the attorney general during the Bush administration.

Mukasey is also former Fox News chairman Roger Ailes' attorney and represented him when Ailes faced multiple allegations of sexual harassment toward female employees at Fox News. Ailes later resigned from his position as the allegations gained nationwide coverage.

Bharara, at the time of his firing, was in the midst of an investigation into Fox News relating to its business practices when it was led by Ailes. Trump fired Bharara on the heels of a segment during which Fox News host Sean Hannity advocated for a "purge" of all Obama-appointed Justice Department officials.

Getty Images

Edward O'Callaghan

Edward O'Callaghan

O'Callaghan assisted the Trump transition team and is currently a partner specializing in white-collar defense at Clifford Chance. He also worked as a federal prosecutor and co-chief of the terrorism and national security unit at the US attorney's office in New York before resigning in 2008 to work on Sen. John McCain's presidential campaign.

While working on McCain's campaign, O'Callaghan became part of what the campaign called a "truth squad," formed to provide legal cover and pushback against ethics charges brought against then-vice presidential candidate Sarah Palin. At the time, he spearheaded an effort to quash the pre-election investigation - which became known as "Troopergate" - into Palin when she was governor of Alaska.