President Trump on Wednesday praised his former campaign chairman who was just convicted of defrauding the federal government and accused his longtime personal attorney of breaking under legal pressure.

Paul Manafort, Mr. Trump’s former campaign chairman, was convicted Tuesday of tax and financial fraud. Michael D. Cohen, the president’s former personal lawyer and fixer, made a plea agreement with federal prosecutors and admitted to campaign finance crimes that he said were committed at the direction of Mr. Trump.

In the president’s view, Mr. Manafort is “brave,” and Mr. Cohen is a bad lawyer who, Mr. Trump incorrectly asserted, pleaded guilty to “violations” that “are not a crime.”

Mr. Trump said he felt bad for Mr. Manafort and his family. And he warned his nearly 54 million Twitter followers not to hire Mr. Cohen.

Mr. Trump’s comments in the series of Twitter posts Wednesday morning appeared to be a reminder to others who might consider implicating him that he highly values loyalty.

Democrats seized on Tuesday’s guilty plea and verdict, raising the stakes of the midterm congressional elections in November and throwing roadblocks in front of the confirmation of Mr. Trump’s Supreme Court nominee, Brett M. Kavanaugh. The president’s fate rests with Congress. If Democrats win back the majority in the House, impeachment proceedings against the president could begin next year.

“It’s a game changer,” Mr. Schumer, of New York, said in a tweet about Mr. Cohen’s implication of Mr. Trump in his campaign finance crimes.

Mr. Cohen on Tuesday admitted that Mr. Trump had a role in payments made during the 2016 presidential campaign to two women who said they had affairs with Mr. Trump. In the plea agreement, Mr. Trump is not mentioned by name, but referred to as “Individual-1.”

Mr. Cohen and his attorney have made clear that, if asked, Mr. Cohen would cooperate with the continuing special counsel investigation into Russian interference in the 2016 election, an investigation Mr. Trump on Wednesday again called a “Witch Hunt.”

Mr. Trump has previously dismissed the gravity of campaign finance violations. In May, he pardoned a best-selling author and documentarian of the crime, saying the defendant, Dinesh D’Souza, was not treated fairly by the justice system. The move was seen by many as a not-so-subtle message to Mr. Cohen that he too could receive a presidential pardon for campaign finance crimes.

In addition to the campaign finance crimes, Mr. Cohen pleaded guilty to tax evasion and bank fraud, but his agreement with federal prosecutors may have saved him from decades in prison. Instead, he is likely to be incarcerated for only a few years.

Prosecutors said that Mr. Cohen’s $130,000 payment to the pornographic actress Stephanie Clifford, better known as Stormy Daniels, was a donation to Mr. Trump’s presidential campaign because it secured her silence about a possible affair to help his odds of winning the election. Campaign finance laws prohibited donations of more than $2,700 in the 2016 general election.

Mr. Cohen also admitted to “causing” an illegal corporate donation to Mr. Trump because of his involvement in a $150,000 payment to another woman, Karen McDougal, who said she had an affair with the candidate.