Author and “Morning Joe” mainstay Jon Meacham compared President Trump’s desire to build a wall along the southern border to Ku Klux Klan rhetoric from nearly 100 years ago.

“America should ‘build a wall of steel, a wall as high as Heaven’ against the flow of immigrants.-- Georgia Gov. Clifford Walker, at a 1924 convention of the Ku Klux Klan, then a powerful force at a time of strain for the white working class,” Meacham wrote before adding “#PastIsPrologue.”

Meacham, a frequent panelist on MSNBC’s morning show, has been extremely critical of Trump. This time, he quoted Walker, a Democrat who served as governor from June 30, 1923, to June 25, 1927, and had strong ties to the KKK.

Democrats have financed steel barriers in the past, but Trump has made a more complete barrier a key issue of his presidency. Trump used his first-ever prime time address from the Oval Office on Tuesday night to make his case for funding a southern border wall.

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At one point Trump said people “don’t build walls because they hate the people on the outside,” but instead because “they love the people on the inside."

“Notice the selective nature of today's media. When Democrats like Hillary Clinton and Chuck Schumer promoted a wall, no one on the left or in the media made a peep. Now that it's Trump, suddenly they tie it to the KKK,” Media Research Center Vice President Dan Gainor told Fox News.

“Trump could come out today and endorse the entire Democrat platform from 2016 and the media would be up in arms and opposing it by noon,” Gainor said.

MSNBC did not immediately respond to a request for comment.

Meacham is an award-winning presidential historian who has penned books on Thomas Jefferson, George H.W. Bush and Andrew Jackson, among others. He isn’t the only “Morning Joe” regular to attack Trump over Tuesday’s Oval Office address, as co-host Willie Geist implied that the president is not mentally fit for office.

“The networks and Democrats, everybody is acting as if he is fit, taking part in this colossal waste of time, which would be this presidency, instead of looking at it instead of saying, this person is not fit to lead, and acting on that I’m not sure why it’s happening,” Geist said on Wednesday’s edition of the MSNBC morning show, according to Mediaite.

Fox News’ Gregg Re contributed to this report.