For 40 years, first-term presidents have been leading a ceremony at the White House to unveil the portrait of the president that preceded them. President Donald Trump, however, has chosen not to continue that tradition. 

According to NBC News, Trump has decided not to hold a ceremony for the unveiling of Barack Obama's portrait. However, Obama wouldn't be interested in attending the ceremony even if there was one, sources told NBC News.

The relationship between Obama and Trump, which has been strained for a while, took an even bigger hit in recent days. Trump most recently fueled baseless allegations against Obama, suggesting that the 44th president has committed a crime, but failing to explain what exactly the crime was.  

"I have no doubt that they were involved in this hoax, one of the worst things ever to befall this country in terms of political scandal," Trump said to reporters on Monday without giving any explanation.

Obama fired subtle shade at the sitting president during his speeches at two virtual graduation ceremonies over the weekend. As Blavity previously reported, the 44th president said the coronavirus "has revealed the glaring inadequacies of America's current leadership."

"All those adults that you used to think were in charge and knew what they were doing? It turns out that they don't have all the answers," Obama said during Saturday's broadcast of "Graduate Together: America Honors the High School Class of 2020." "A lot of them aren't even asking the right questions. So, if the world's going to get better, it's going to be up to you."

The 45th responded by calling Obama an "incompetent president."

"That's all I can say," Trump told reporters. "Grossly incompetent."

All the back and forth has now caused a rift in a long-standing American tradition that typically follows a specific process.  According to NBC News, the process of unveiling a president's portrait starts with the former president and first lady choosing the artist for the picture.

After the first couple approves of the finalized portrait, it gets delivered to the White House and the ceremony is scheduled. The former president's staff, family and friends typically join White House officials during the unveiling. 

"Presidential portrait unveilings are one of the three events that bring former presidents together. This level of animosity between a sitting president and his predecessors is unprecedented in modern history," Kate Andersen Brower, author of Team of Five: The Presidents Club in the Age of Trump, told CNN.

Obama graciously led the ceremony for former President George W. Bush in 2012.

"The months before I took the oath of office were a chaotic time. We knew our economy was in trouble, our fellow Americans were in pain, but we wouldn’t know until later just how breathtaking the financial crisis had been," Obama said at the unveiling in 2012.

"And still, over those two and a half months — in the midst of that crisis — President Bush, his Cabinet, his staff, many of you who are here today, went out of your ways — George, you went out of your way — to make sure that the transition to a new administration was as seamless as possible," Obama added.

Earlier this month, CNN anchor Don Lemon pondered aloud what exactly it is about the previous POTUS that appears to bother Trump. 

“What is it about President Obama that really gets under your skin? Is it because he’s smarter than you?" Lemon said. "Better educated? Made it on his own — didn’t need Daddy’s help?"

"Wife is more accomplished? Better looking?" the CNN anchor continued to ask. "I don’t know, what is it, what is it about him? That he’s a Black man that’s accomplished being president? That he punked you on the whole birth certificate thing? What is it about him? Just wondering.”