Trump has floated delaying the presidential election, and made false claims that mail ballots are fraudulent and that he lost the popular vote in 2016 because of ballots cast by millions of undocumented immigrants.

Sanders is planning a series of actions aimed at raising awareness of the possibility of Trump resisting leaving office if he does not win. The senator will give a speech on the issue in the near future, and send an email to his massive list of supporters about the topic on Friday.

“What we have got to do in the next two months is to alert the American people about what that nightmarish scenario might look like in order to prepare them for that possibility and talk about what we do if that happens,” he said.

According to an embargoed copy of his coming email, Sanders is planning to state, “This is not just a ‘constitutional crisis.’ This is a threat to everything this country stands for."

Sanders is also going to lay out in his message to his supporters a series of steps that should be taken now to prepare for the election. He will say news organizations need to alert people that the election results may not be known on Nov. 3. Social media companies “must finally get their act together” to ensure that election officials are not harassed and disinformation is not spread on their platforms, he said.

Additionally, he called for congressional hearings with local officials about their plans for Election Day and thereafter. He also said state legislatures in Pennsylvania and elsewhere must pass bills to allow election officials to begin counting mail ballots before the election.

Sanders said he is worried about what some Democratic strategists have called a “red mirage”: The appearance of a Trump lead on the night of the election in some battleground states, even if he lost, due to the fact that Republicans are more likely to vote in person, whereas many Democrats are planning to vote using mail ballots, which will take longer to count.

“The nightmare scenario there is that, at a time when some states like Pennsylvania are finding that they don’t have the resources right now to count votes, their mail-in ballots, in a rapid way, that it is possible that in some states Trump will be winning on election night, and yet when all of the votes are counted, he will be behind. He will lose,” Sanders said of Trump. “But that during that interval, he will create chaos and confusion by claiming that there is massive fraud within the mail-in ballot process.”

Sanders is not the only one who is worried about Election Day. Former Philadelphia Mayor Michael Nutter said he raised concerns about the possibility of a red mirage in Pennsylvania with Gov. Tom Wolf’s office. The Transition Integrity Project, a bipartisan group, has also led a series of war-game exercises about different election scenarios and released a report that said “Trump is likely to contest the result by both legal and extra-legal means, in an attempt to hold onto power.”

Sanders said he spoke a week ago to Rosa Brooks, co-founder of the organization, and she is “doing exactly the right thing.”

Sanders, who had a highly active group of volunteers during his two presidential campaigns, declined to answer whether he would call on his supporters to hit the streets if Trump refused to leave office, saying, “I don’t want to speculate about what happens the day after the election.”

Speaking earlier this year about what would happen if Trump refused to leave office after losing, Joe Biden said, "I promise you, I'm absolutely convinced they will escort him from the White House with great dispatch.” But Chairman of the Joint Chiefs of Staff Gen. Mark Milley told Congress in comments made public last month that the military will not resolve disputes if the election is contested.

Asked if that concerns him, Sanders said, “it does.”

“Because there is a very high likelihood that Trump will contest the results if he loses,” he said. “And it would be an unprecedented moment in American history and undermining everything that this country stands for if we have a president remain in office who lost the election.”

Sanders added: “I certainly hope with all of my heart that none of this happens.”

Republican National Committee spokesperson Michael Joyce dismissed Sanders’ concerns.

"The only reason Bernie Sanders is spreading hypothetical conspiracy theories about President Trump is because even an avowed socialist like Bernie realizes that Joe Biden’s radical left agenda is going to cost him the election on Nov. 3,” he said.