Flynn quit after after news reports revealed that former acting Attorney General Sally Yates had warned McGahn's office late last month that Flynn had misled officials about details of his conversations with the Kremlin's US ambassador Sergey Kislyak and could be vulnerable to Russian blackmail.
Questions immediately arose about McGahn's handling of the situation: What exactly did he do with the information from the Justice Department; were White House Chief of Staff Reince Priebus and President Donald Trump told, and if so, when; and if they were told, what resolution was ultimately reached that allowed Flynn to keep his job for weeks after Yates' revelation?
McGahn's office referred questions to the White House press office, which did not respond.
But on Tuesday, White House Press Secretary Sean Spicer told reporters that Yates merely wanted to give McGahn a "heads up" and that McGahn "informed the President immediately."
McGahn conducted "exhaustive and extensive questioning of Flynn," according to Spicer, and McGahn concluded that Flynn had not violated the law.
A former campaign finance lawyer by trade, McGahn now finds himself in the midst of a high-profile political firestorm with a client that blasts out tweets in the early hours of the morning on the very hot-button topics McGahn has been tapped to manage.
To say that McGahn has his work cut out of him is therefore, an understatement. The news of Flynn's departure also comes on the heels of a series significant losses in federal court over the President's travel ban and the Office of Government Ethics recommending on Tuesday that the White House consider launching an investigation and taking "disciplinary action" against Kellyanne Conway, a top adviser to Trump, for endorsing Ivanka Trump's products on TV last week.
Election litigator turned chief White House lawyer
Prior to working at 1600 Pennsylvania Avenue, McGahn was a partner specializing in campaign finance at Jones Day in Washington, general counsel for Trump's campaign, in-house counsel for the National Republican Congressional Committee for years and former chairman for the Federal Election Commission from 2008-2013.
"He rewrote virtually all of the FEC's procedures for audits, enforcement matters and advisory opinions, which provide for an unprecedented amount of due process," according to a statement
from Jones Day announcing his departure from the firm.
More than simply an aggressive litigator, he also has been known to have a flair for the dramatic at times. Once while at the FEC, he tore pages of regulations out of book at a public hearing to drive home his point during a rant against his Democratic colleagues.
And unlike many of his straitlaced former colleagues who display diplomas from their Ivy League law schools on their walls, McGahn went to Pennsylvania's Widener University, used to keep his hair relatively long and played in an '80s cover band, according to a Washington Post profile
"Don has a brilliant legal mind, excellent character and a deep understanding of constitutional law," Trump said in a statement announcing his appointment as White House counsel back in November. "He will play a critical role in our administration, and I am grateful that he is willing to serve our country at such a high-level capacity."