Donald Trump has mocked his opponents, asking "where is the collusion?", hours after his former campaign manager was found guilty of tax fraud.
Paul Manafort was found guilty of eight out of 18 charges relating to financial crime.
It came as Mr Trump's former lawyer Michael Cohen admitted paying hush money to a porn actress and a model to influence the US Presidential campaign.
But the president said the jury's verdict on Manafort and Cohen's pleas were nothing to do with alleged collusion with Russia before the 2016 US presidential election.
As he arrived at a rally in West Virginia he told reporters: "It's a very sad thing that happened, this has nothing to do with Russian collusion.
"He worked for many, many people.
"I must tell you that Paul Manafort is a good man. He was with Ronald Reagan, he was with a lot of different people over the years, and I feel very sad about that."
During the rally, he asked supporters: "Where is the collusion? Where is it?
"They are still looking for collusion, where is the collusion? Find some collusion. We want to find the collusion."
One source called the revelations a "bad day for the home team" while others fear the news will hurt the Republican party's midterm prospects.
Norman Eisen, chair of Citizens for Responsibility and Ethics in Washington and a former Barack Obama adviser, tweeted: "In a nutshell, today was the worst day of Trump's life–but only so far…."
Cohen, who was fired in May this year, agreed to plead guilty to one count of wilfully causing an unlawful corporate campaign contribution and one count of making an excessive campaign contribution.
Cohen said that he made the payments "at the direction" of a candidate for federal office. Mr Trump was not named in court but the dates and amounts detailed align with payments made to Ms Daniels and Ms McDougal in the months leading up to the presidential election.
Cohen said one payment was made "in co-ordination and at the direction of the candidate for federal office" and another was made "under the direction of the same candidate".
He added that the money was paid "for the principal purpose of influencing the election".
Deputy US attorney for the southern district of New York Robert Khuzami said invoices for the payments were made to Mr Trump's company.
Rudy Giuliani, Mr Trump's current lawyer, said the payments had been made to spare the Trump family embarrassment and were separate to the campaign.
Cohen's plea agreement raises the possibility that he will be required to provide information to special counsel Robert Mueller's Russia probe.
Mr Trump has been fighting a rearguard action against allegations members of his circle colluded with Russian officials to influence the 2016 election.
CNN has reported that Mr Cohen's plea deal includes prison time for the president's long-time fixer, with Fox News suggesting he will be handed a three- to five-year jail term.
Meanwhile, the president's former campaign manager Manafort was convicted of five counts of filing false income tax returns, one count of failing to file a report of a foreign bank account in 2012 and two counts of bank fraud.
Judge Thomas Ellis declared a mistrial on the 10 other charges after jurors failed to reach a unanimous verdict.
The jury deliberated for four days before announcing the verdict at the federal courthouse in Alexandria, Virginia.
It is the first trial victory for special counsel Robert Mueller's team.
The judge declared the court is in recess following the verdicts.
Judge Ellis has not set a sentencing date and has given prosecutors until 29 August to decide whether to retry Manafort on the deadlocked charges.
The trial is the first of two for Manafort.
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He faces a trial later this year in the District of Columbia on charges of conspiracy against the United States, conspiracy to launder money, making false statements and acting as an unregistered foreign agent for Ukrainian interests.
He is also accused of witness tampering in that case.