Senator Chuck Schumer, Democrat of New York and the minority leader, has said senators should hear from senior administration officials who refused to testify during the House impeachment investigation. Those include Mick Mulvaney, the acting White House chief of staff, and John R. Bolton, the former national security adviser who, according to his lawyer, knows about “many relevant meetings and conversations” on Ukraine.

Speaker Nancy Pelosi said this week that Democrats would not deliver the two approved articles of impeachment to the Senate until they agreed to fair procedures for the trial. As lawmakers left Washington in recent days, Senator Mitch McConnell of Kentucky, the majority leader, said the two sides “remain at an impasse.”

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Before arriving at his Mar-a-Lago estate in Palm Beach, Fla., late Friday, Mr. Trump denounced his impeachment on Twitter and vowed to seek vindication in the Senate. On Friday, he tweeted that he “never did anything wrong. Read the Transcripts. A Democrat Hoax!”

He also blasted a conservative Christian magazine for publishing an editorial calling for his removal from office. Mark Galli, the editor of the magazine, Christianity Today, wrote that Mr. Trump had tried to coerce a foreign leader to discredit one of his political opponents.

“That is not only a violation of the Constitution; more importantly, it is profoundly immoral,” Mr. Galli wrote. On Twitter, the president excoriated the magazine as “far left,” saying it “would rather have a Radical Left nonbeliever, who wants to take your religion & your guns, than Donald Trump as your President.”

But in his remarks on Saturday, Mr. Trump appeared determined to dismiss the impeachment inquiry — which dominated much of the political debate over the last two months — as a failed political attack by his rivals.

“There’s no crime. There’s no nothing. How do you impeach when you have no crime?” the president asked the crowd, referring briefly to Ms. Pelosi as “crazy Nancy” and insisting that she had no case against him. “It’s so unfair.”