MSNBC political analyst John Heilemann claimed on Tuesday that President Trump's deployment of federal agents into Portland was a "trial run" for what is to come beyond the 2020 election.

The Department of Homeland Security has been under fire in recent days after footage from the protests and riots in Portland show hostile confrontations with federal agents, including a video showing them making arrests in unmarked vans.

Appearing on MSNBC's "Morning Joe," Heilemann declared the use of such militarized agents on the ground "authoritarianism."

"These are the kinds of things we have seen in tyrannical, authoritarian regimes in third-world countries throughout the 20th- second half of the 20th century," Heilemann explained. "This is not a mystery what's going on here and I think that to look at this through the prism of symbolic politics, the law and order campaign, Trump trying to rerun the Nixon playbook, is true but doesn't, as I say, go far enough."

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The commentator told the panel that it is time to be "an alarmist," looking at Trump's weakened standing heading into November.

"I think we are looking at potentially a trial run for a kind of, a genuine attempt to, through intimidation and potentially through force, to try to steal this election," the MSNBC analyst said. "I think we are now at the point where, you know, we see what the president is doing, we see his intention to not accept an outcome of this election where he loses to Joe Biden. He is making it very clear."

He went on to warn Democrats that Trump could send troops to major cities as a "dress rehearsal" in an attempt to intimidate voters.

"In those two-and-a-half months after Election Day until January 20, if Donald Trump has lost this election, the things we're seeing right now, these incredibly alarming, incredibly disturbing images -- unmarked paramilitary units that have no clear chain of command, no clear identification, taking protesters and putting them in unmarked vehicles driving them away to God knows where, we should all be kind of freaking out about this right now and what it could portend for this fall and beyond," Heilemann continued.

"I think you put it pretty perfectly, John Heilemann," Mika Brzezinski reacted.

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Former Obama Attorney General Eric Holder was later asked by "The ReidOut" host Joy Reid if he was "concerned" about what her MSNBC colleague predicted.

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Holder responded "we have to be prepared" for what the president will do following his defeat in November.

"We have to be prepared for things that this nation has never faced before. And unfortunately, that could involve the use of these forces," Holder told Reid. "Who knows what he'll do and the people as part of his administration will support him in doing."