Aiken's change of heart was evidently prompted by Trump's Tuesday afternoon press conference at Trump Tower, in which he blamed the violence at the Charlottesville, Virginia, alt-right rally on both the white supremacists and the "alt-left" counter-protesters; argued that there were some "fine people" mixed in with the neo-Nazis and condemned the removal of a statue honoring Confederate general Robert E Lee, whom he equated to George Washington and Thomas Jefferson.
In a fellow-up tweet, Aiken clarified that he "always thought he [Trump] would be a dumpster fire as a president."
"I just didn't think he was racist. #wrong," Aiken added.
When another Twitter user criticised Aiken for ignoring the many warning signs about Trump, the American Idol runner-up became defensive and reminded his critics that he spoke out against then-candidate Trump throughout the campaign, and even urged people to vote for Hillary Clinton.
Aiken, who made an unsuccessful run for Congress as a Democrat in his home state of North Carolina in 2014, became indignant and lashed out when another commenter labelled him a Trump supporter.
"B****, please! If you think I have EVER been a 'Trump supporter' you're as crazy as he is. #payattention," Aiken protested.
He wrapped up his Tuesday evening tweet-storm with a post summing up his views on Trump: "My party is the Democrats. I didn't vote for the idiot. Never ever implied that I did or would. Was VERY vocal about not voting for him".
It was not the first time that Aiken publicly criticised Trump.
In an interview on a North Carolina News and Observer podcast last month, Aiken, who competed on the Celebrity Apprentice in 2012 and came in second, losing out to Arsenio Hall, painted an unflattering portrait of the billionaire businessman as a clueless play-actor.
Aiken claimed that Trump was not the one who was deciding whom to ax on the reality show; instead, he would get the name of the contestant slated for firing from NBC producers via a teleprompter.
"I think to myself, the man as president definitely has a teleprompter sitting on his desk right now with people telling him, 'Well such and such is in the healthcare bill, don't say this'," Aiken told the paper.
"I feel like half the time his teleprompter has broken down as president and he doesn't know what's going on."
