U.S. Rep. Gwen Moore contends her colleagues should consider bringing U.S. Sen. Ron Johnson before the House Intelligence Committee as part of its impeachment inquiry because he asked President Donald Trump in August about withholding aid to Ukraine.

And the Milwaukee Democrat is also making the case for getting rid of Trump by having his own cabinet invoke the U.S. Constitution's 25th Amendment. The amendment allows the vice president to take over if a majority of the cabinet deems the president incapacitated.

"This man is an authoritarian. He's a totalitarian," Moore told reporters Wednesday in Milwaukee. "Impeachment can't come quickly enough and I would love to see the 25th Amendment invoked right now."

In an interview, Moore said Johnson may need to be interviewed as part of the House's impeachment inquiry because he was alerted in August by an ambassador that nearly $400 million in aid to Ukraine was being withheld because Trump wanted the country to launch an investigation that would help him politically.

The GOP senator from Wisconsin has said the president denied that the aid and investigation were linked. Johnson in recent days has defended the president for having an interest in investigating a theory among some conservatives that Ukraine played a role in the 2016 U.S. election.

“He believed the president, even though he had heard from a source that’s reliable to him, (U.S. Ambassador to the European Union Gordon) Sondland, that there was, in fact, a quid pro quo,” Moore said.

“It means that Ron Johnson is complicit. It means that his butt perhaps needs to appear before the Intelligence Committee to offer some testimony too.”

The impeachment inquiry centers on whether Trump kept back the aid to pressure Ukraine to investigate the 2016 election and former Vice President Joe Biden, who is seeking the Democratic nomination for president.

Johnson acknowledged last week that Sondland told him in August that the aid and investigations were linked. He told the Wall Street Journal he “winced” when he heard that and confronted Trump about it the next day. Johnson said Trump denied it and Johnson believed his denial.

Johnson defended Trump in a contentious appearance Sunday on NBC’s “Meet the Press,” where Johnson stressed the need to investigate a conspiracy theory that Democrats worked with Ukraine to plant a claim that Trump’s campaign colluded with Russians in the 2016 election.

"Either he’s bought into these conspiracy theories or he's promoting them to confuse people, to deliberately confuse people, to maintain support for the president,” Moore said. “Either way, it is unbecoming of a United States senator who is chairman of the Homeland Security Committee and on the Foreign Relations Committee.”

She contended Johnson would hurt his political legacy by backing Trump so vehemently.

“When I think back on the McCarthy days and think about things that I'm ashamed of in this state, I have to add Ron Johnson to that list,” she said, referring to Joe McCarthy, the red-baiting senator from Wisconsin whose career ended in infamy.

She added: “I'm not saying that he’s a Joe McCarthy, but he’s pushing conspiracy theories.”

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Johnson indicated Sunday on WISN-TV’s “UpFront” that he would cooperate if investigators asked for his assistance.

"I would certainly cooperate," he said. “I have no idea — obviously, I have firsthand knowledge."

Johnson spokesman Patrick McIlheran said Wednesday that Johnson has not been contacted by the House Intelligence Committee but will cooperate if he is.

An aide to Rep. Adam Schiff, the California Democrat who leads the Intelligence Committee, did not respond to a question about whether Schiff would seek testimony from Johnson.

At her Milwaukee stop Wednesday, Moore advocated for a fast impeachment, as well as having the 25th Amendment invoked.

"I want to see it invoked because I think he's dangerous," she told reporters. "I think he's maladjusted. I think he is mercurial. I think that he is not listening to anyone and I am concerned about our national security."

Patrick Marley reported from Madison and Bill Glauber reported from Milwaukee.

Contact Patrick Marley at patrick.marley@jrn.com. Follow him on Twitter at @patrickdmarley.