Over the weekend the president tweeted, "I will be there. Historic day!" replying to a tweet from one of the rally organizers.
Trump's plan to attend Wednesday's rally comes on the heels of audio surfacing of a Saturday phone call he had with Georgia Secretary of State Brad Raffensperger in which the president demanded Raffensperger "find" the exact number of votes he would need to be declared the winner in Georgia, despite three separate counts confirmed that he lost.
"The people of Georgia are angry. The people of the country are angry, and there's nothing wrong with saying that, you know, that you've recalculated," Trump told Raffensperger on the call. "All I want to do is this: I just want to find 11,780 votes, which is one more than we have."
President-elect Joe Biden won the state by 11,779 votes.
Many close advisers to the president were "beside themselves" and unaware of the call's existence until the story was published first by the Washington Post Sunday evening, sources told ABC News.
The sources say Trump is increasingly isolated, describing a man who is only interested in the Electoral College certification process in Congress on Jan. 6.
Even loyalists who have thus far publicly supported the president's false claims that the election was stolen from him have begun to think about job opportunities in a post-Trump world -- but they have been unable to discuss with Trump whether they will still work for him outside of the White House, sources say.
"We are still in the denial phase," said one Trump ally, who described Trump's plans between Jan. 6 and Biden's inauguration on Jan. 20 as "unknown."
Nevertheless, one of the few remaining fully-staffed offices in the White House is the White House Counsel's Office, which continues to vet the growing list of potential pardons for the president to grant in his last days in office. The final rounds of pardons are expected to come in waves during Trump's last weeks, with some coming as soon as this week, sources said.
And while Trump may not be discussing it publicly, the president still plans to spend his post-presidency life in Florida.
As he spent the Christmas holiday at his private Mar-a-Lago Club in Palm Beach, Trump fumed about renovations to his living quarters, according to sources familiar with his mood.
Trump, along with first lady Melania Trump and their son Barron, had been planning to make the club their full-time home, but due to space concerns and threats from local officials claiming the club cannot be used as a full-time residence, those plans could change.
Sources say the Trumps have begun considering purchasing a home in the Palm Beach area that would not be on the Mar-a-Lago grounds.