Historian and Lyndon B. Johnson Foundation CEO Mark Updegrove said on Tuesday that "Unpresidented" would be an apt title for a book about President Trump Donald John TrumpSteele Dossier sub-source was subject of FBI counterintelligence probe Pelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' Trump 'no longer angry' at Romney because of Supreme Court stance MORE's time in the White House because of of his "unprecedented" approach to the presidency.

"I think if you are to write the book about this president, it would be called 'Unpresidented' because we're seeing some unprecedented things in the office of the president," Updegrove told Hill.TV's Krystal Ball and Lawrence Jones on "Rising."

"One of the things is we are seeing a president fan the flames of division," Updegrove said. "He is intentionally divisive and seems constitutionally incapable of putting the needs of the country above his own."

"All [you] had to do is walk by the White House, which I did yesterday, and see that flag flying at full mast," he added, referring to the White House flag being returned to full staff less than 48 hours after Sen. John McCain John Sidney McCainAnalysis: Biden victory, Democratic sweep would bring biggest boost to economy The Memo: Trump's strengths complicate election picture Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' MORE (R-Ariz.) died. "If you can't honor a hero like John McCain, it really shows you're not thinking about the country."

The White House later on Monday re-lowered the flag to half-staff after facing backlash.

Trump and McCain maintained a contentious relationship ever since Trump launched his campaign in 2015.

Various books have been published detailing the first part of Trump's presidency, including Michael Wolff's "Fire and Fury: Inside the Trump White House" and former White House aide Omarosa Manigault Newman Omarosa Onee Manigault NewmanTrump hurls insults at Harris, Ocasio-Cortez and other women Pelosi makes fans as Democrat who gets under Trump's skin The Memo: Impeachment's scars cut deep with Trump, say those who know him MORE's "Unhinged: An Insider's Account of the Trump White House."

Journalist Bob Woodward is set to release a book on the Trump presidency on Sept. 11 titled, "Fear: Trump in the White House."

— Julia Manchester