Trump lifted off from the White House in Marine One to catch a flight to Lake Charles, Louisiana, telling reporters the impeachment investigation is "a hoax."
Polls show growing public support for the probe into Trump's request for Ukraine to push a corruption case against one of his main Democratic opponents in the 2020 election, Joe Biden.
He is only the fourth US president to face an impeachment probe but after an initially stumbling response, the Republican has hit on a strategy of maximum resistance to trying to transform the threat into a boost.
But despite White House attempts to stop witnesses from appearing before congressional investigators, former ambassador to Ukraine Marie Yovanovitch, who was fired by Trump, testified before three House committees on Friday.
Trump blocks impeachment probe witness, Democrats claim obstruction
According to The New York Times, she told legislators that she was forced from her job as a result of "false claims."
There was possibly worrying news for Trump as troubles mounted for his colorful, but controversial personal attorney Rudy Giuliani, a central figure in the administration's murky contacts with Ukraine.
Congressional investigators see Giuliani as Trump's point man in a campaign to extract dirt on Biden from the Ukrainians. On Wednesday, two of the lawyer's clients were arrested in a campaign finance violation case involving foreign money.
Asked on Friday if Giuliani continued to be his lawyer, Trump gave a less than convincing answer.
"I don't know," he said. "He's a very good attorney and he has been my attorney."
Trump's previous personal attorney Michael Cohen was sentenced to three years in prison in 2018.
Trump's Louisiana rally comes after he barnstormed a gathering in Minneapolis, Minnesota on Thursday, vowing a "backlash" against Democrats.
Trump to host first post-impeachment inquiry rally in Democratic stronghold
In a speech lasting an hour and 40 minutes, Trump said his opponents were "getting desperate."
"They want to erase your vote like it never existed, they want to erase your voice and they want to erase your future, but they will fail because in America, the people rule again."
The "insane impeachment witch hunt" will fail, the Republican told the sea of campaign-branded red shirts and hats.
And in 2020 this will "produce a backlash at the ballot box the likes of which they have never ever seen before."
The speech featured aggressive language against leftist Somali-American congresswoman Ilhan Omar, who represents Minneapolis, Biden and his son Hunter, and the media.
Leading the crowd in extended booing against journalists in the stadium, Trump called them "crooked writers" and "fakers."
And he said that Biden had only been considered a success as vice president "because he understood how to kiss Barack Obama's ass."
Democrats who have accused Trump of abusing his office throughout his first term believe they have finally cornered the president with the impeachment probe.
Trump was shown in the rough transcript of a phone call summary issued by the White House to have pressed new Ukrainian President Volodymr Zelensky to open a corruption probe of Biden and his son.
The president has pushed back, refusing to allow anyone in his administration to cooperate with the impeachment inquiry.
Public support for impeachment, though, is increasing. A poll from Fox News - a channel favored by US conservatives - shows 51 per cent back his removal from office.
With control of the lower house of Congress, Democrats are likely to vote to impeach in the coming months, even if few believe the Republican-led Senate will actually convict Trump and force him from office.
However, Trump has faced a rare party rebellion this week over his abrupt decision to remove US troops from the Turkish-Syrian border, effectively abandoning Kurds who had fought alongside the United States in Syria to a Turkish assault.
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