The former Bush 43 press secretary said on "Squawk Box" that he dealt with "Bush derangement syndrome on a daily basis," when the former Texas governor occupied the White House.
The hatred for Trump "is triple that," said Fleischer, who served as White House spokesperson during the historic 2000 presidential election recount, on Sept. 11, 2001, and during the wars in Iraq and Afghanistan.
The left's loathing of Bush started when "he won," Fleischer said, referring to the legal battle that ended with Democrat Al Gore conceding the electoral college. The final count was Bush 271 to 266.
While Gore in 2000 and Hillary Clinton in 2016 edged out their Republican opponents in the popular vote, Trump, like Bush, won where it mattered, the electoral college, with 306 to the former secretary of State's 232 votes.
According to Gallup's daily presidential approval poll, Trump's disapproval rating hit 51 percent on Saturday, eight days after taking office. That's the fastest move ever to a majority disapproval.
Bush hit a majority disapproval six months into his second term, as the Los Angeles Times pointed out, and remained in negative territory for the rest of his time in the White House.
Looking at the anger directed at Trump, "he created part of it" with poor messaging, said Fleischer, currently head of the communications company that bears his name.
Case in point, he argued was the rough implementation of Trump's controversial executive order temporarily banning travelers from entering the U.S. from seven Muslim-majority countries.
Trump moved too quickly and did not coordinate properly with Homeland Security Secretary John Kelly, Fleischer said.
Fleischer said he suspects Kelly, a retired general, is communicating to the White House: "You just took your mulligan," using a golf term for taking a do-over shot.