LAKE CHARLES, Louisiana — As impeachment pressure mounted on Donald Trump, the president left Washington for the second day in a row Friday to rally hardcore supporters in a bid to turn the scandal into fuel for his 2020 reelection.

Framing himself as the victim of a plot between "corrupt Democrat politicians" and the "fake news media," Trump galvanized supporters at a rally in Lake Charles, Louisiana.

In provocative comments to an enthused base Trump insisted his Democratic rivals — who are leading the investigation against him in the House — were "pursuing an illegal, unconstitutional, bullshit impeachment."

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 trying to transform the threat into a boost.

Trump attacked House Speaker Nancy Pelosi with particular gusto, telling the crowd her support for the impeachment investigation was evidence of disdain for the United States: "I used to think she loved the country. She hates the country," he said.

Turning his attention to next year's election, Trump said he was convinced he would win in 2020, no matter what.

"Looks like Bernie lost his chance, huh?" Trump said, in apparent reference to Vermont Senator Bernie Sanders, a 2020 Democratic contender who suffered a recent heart attack.

Trump's Louisiana rally comes after he barnstormed a gathering in Minneapolis, Minnesota on Thursday, vowing a "backlash" against Democrats.

"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."

And in 2020 this will "produce a backlash at the ballot box the likes of which they have never ever seen before."

Back in Washington, former ambassador to Ukraine Marie Yovanovitch, who was fired by Trump, testified before three House committees on Friday, despite White House attempts to stop witnesses from appearing before congressional investigators.

She told legislators that she was forced from her job as a result of "false claims," according to The New York Times.

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 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 prison in 2018. -AFP