Michael D. Cohen, President Trump’s former lawyer, made the extraordinary admission in court on Tuesday that Mr. Trump had directed him to arrange payments to two women during the 2016 campaign to keep them from speaking publicly about affairs they said they had with Mr. Trump.
Mr. Cohen acknowledged the illegal payments while pleading guilty to breaking campaign finance laws and other charges, a litany of crimes that revealed both his shadowy involvement in Mr. Trump’s circle and his own corrupt business dealings.
He told a judge in United States District Court in Manhattan that the payments to the women were made “in coordination with and at the direction of a candidate for federal office,” implicating the president in a federal crime.
“I participated in this conduct, which on my part took place in Manhattan, for the principal purpose of influencing the election” for president in 2016, Mr. Cohen said.
The plea represented a pivotal moment in the investigation into the president, and the scene in the Manhattan courtroom was striking. Mr. Cohen, a longtime lawyer for Mr. Trump — and loyal confidant — described in plain-spoken language how Mr. Trump worked with him to cover up a potential sex scandal that Mr. Trump feared would endanger his rising candidacy.
Mr. Cohen also pleaded guilty to multiple counts of tax evasion and a single count of bank fraud, capping a monthslong investigation by Manhattan federal prosecutors who examined his personal business dealings and his role in helping to arrange the financial deals with women connected to Mr. Trump.
The plea came shortly before another blow to the president: His former campaign manager, Paul Manafort, was convicted in his financial fraud trial in Virginia. The special counsel, Robert S. Mueller III, had built a case that Mr. Manafort hid millions of dollars in foreign accounts to evade taxes and lied to banks to obtain millions of dollars in loans.
Mr. Trump’s lawyers have, for months, said privately that they considered Mr. Cohen’s case to be potentially more problematic for the president than the investigation by the special counsel.
But Mr. Trump’s lawyer, Rudolph W. Giuliani, said in a statement after Mr. Cohen’s plea, “There is no allegation of any wrongdoing against the president in the government’s charges against Mr. Cohen.”
In federal court in Manhattan, Mr. Cohen made the admission about Mr. Trump’s role in the payments to the women — an adult film actress and a former Playboy playmate — as he pleaded guilty to two campaign finance crimes.
One of those charges stemmed from a $130,000 payment he made to the actress, Stephanie Clifford, better known as Stormy Daniels, in the run-up to the 2016 presidential election.
Prosecutors said that Trump Organization executives were involved in reimbursing Mr. Cohen for that payment, accepting his phony invoices that listed it as a legal expense. The other charge concerned a complicated arrangement in which a tabloid bought the rights to the story about the former Playboy model, Karen McDougal, then killed it.
[The scene inside the courtroom: “I had a glass of Glenlivet 12 on the rocks,” Mr. Cohen said when asked whether he had taken medication or alcohol in the last 24 hours.]
Mr. Cohen’s plea was announced by Robert Khuzami, the deputy United States attorney, along with senior officials from the F.B.I. and the Internal Revenue Service. Addressing reporters outside the courthouse, Mr. Khuzami said that Mr. Cohen had “decided that he was above the law, and for that, he is going to pay a very, very serious price.”