Cohen, once one of Trump's top aides, began talking with the Mueller investigation after he pleaded guilty on August 21 to bank fraud and campaign finance violations in an agreement with New York prosecutors.
"Good for @MichaelCohen212 in providing critical information to the #muellerinvestigation without a cooperation agreement," tweeted Lanny Davis, Cohen's lawyer.
Good for @michaelcohen212 in providing critical information to the #muellerinvestigation without a cooperation agreement. No one should question his honesty, veracity or loyalty to his #family and #country over @potus @realdonaldtrump — Lanny Davis (@LannyDavis) September 21, 2018
The news was originally reported by ABC, which said the 52-year-old New York lawyer and businessman "has participated over the last month in multiple interview sessions lasting for hours" with Mueller's team.
One week ago, former Trump campaign chairman Paul Manafort agreed in a plea deal with Mueller to cooperate in the investigation.
Cohen did not make a commitment to cooperate when he pleaded guilty, but it was clear that cooperation could help him get a lighter sentence.
Mueller is probing whether the Trump election campaign in 2016 colluded with Russian efforts to damage his opponent, Hillary Clinton, and whether Trump has sought to illegally obstruct the investigation.
But the span of the investigation also reportedly encompasses Trump's business dealings, to which Cohen had a front seat during the decade before the election as a senior executive in the president's real estate business in New York, the Trump Organization.
Once known as Trump's "pit bull" right-hand man, Cohen was privy to multi-million-dollar deals and two alleged lovers – whose claims could have potentially sabotaged his boss's 2016 election.
Cohen pleaded guilty to charges involving his arrangement of payouts of hush money to those women – widely thought to be porn star Stormy Daniels and Playboy model Karen Mcdougal – just before the November 2016 vote.
In the plea, Cohen stated that he had acted at his boss's request to buy their silence "with the purpose of influencing the election."
Along with two counts of violating campaign finance laws, Cohen also has pleaded guilty to 6 counts of fraud.
The scandal-prone Trump lambasted his former fixer, accusing him of making up "stories" to cut the plea deal before saying the lawyer's actions were "not a crime" and "not even a campaign violation."
In a Fox interview Trump took aim at his once close associate for "flipping," saying it "almost ought to be outlawed."
Trump conversely praised Manafort for going to trial – the first case stemming from Mueller's probe to go before a jury – and eschewing a plea deal, but he is now also cooperating with the investigation. – Rappler.com