Taken in isolation, Mary Landrieu’s remark about Southern attitudes toward African-Americans can hardly be disputed.

“The South has not always been the friendliest place for African-Americans,” she said in an interview Thursday with NBC News.

Considering the region’s long and bloody history of slavery, lynchings, segregation and overtly racist politicians, that comment is a vast understatement.

But of course, Landrieu’s remark was not delivered in isolation.

To begin with, she’s in the middle of a tough campaign to win her fourth term in the U.S. Senate from Louisiana, and she’s struggling in the polls, which gives her statement a whiff of desperation — especially as the state’s sizable black electorate is her most reliable base of support, and she’s eager to motivate them to vote Tuesday.

Second, the comment was in response to a question about the unpopularity in Louisiana of her fellow Democrat, Barack Obama, the nation’s first black president. Landrieu herself pointed to Obama’s antipathy to a robust pro-energy policy as a major reason for his lack of acclaim in Louisiana before she extended the explanation to include Southern racial thinking. But Obama isn’t unpopular just in the South: He’s pretty unpopular nationwide (although a statement that “the United States has not always been the friendliest place for African-Americans” would be no less true than the one Landrieu delivered).

But likely the biggest problem for Landrieu is the difficulty and reluctance of the South (and the nation) to confront and acknowledge its historical struggles with race, the great crack in the shield of American exceptionalism.

Nowadays, most all Americans regard racism as a vice, and no one likes to consider himself or herself as other than virtuous. Given the undeniable historical record, the standard response to reminders about racism is, “That was then, this is now.”

Sometimes, facts, events or ongoing behaviors may intrude to perturb that comforting belief, such as disparate unemployment, incarceration and sentencing rates, or exclusionary policies by country clubs or Mardi Gras krewes, or a Trayvon Martin or Michael Brown shooting. But although even the most self-congratulatory American might harbor a suspicion, however faint, that, for example, Martin’s and Brown’s chances of being alive today might have been enhanced had they been white, these kinds of things generally can be rationalized away.

Predictably, Landrieu’s Senate election opponents and their fellow Republicans reacted with shock and outrage to what they branded as an insult to the citizens of the very state she represents.

“Senator Landrieu’s comments are remarkably divisive,” the state’s Republican governor, Bobby Jindal, tweeted from his Twitter account. “She appears to be living in a different century.”

Like, maybe, the 20th century — and specifically, 1990.

That was the year of another U.S. Senate election in Louisiana, with another Democratic incumbent, J. Bennett Johnston Jr., facing a challenge from the Republicans.

Longtime state Sen. Ben Bagert, of New Orleans, was backed by the Republican establishment. But his candidacy was soon eclipsed by a rising star in the party: David Duke.

Duke was just in his first year as a state representative from Metairie. He owed his appeal to his past as a grand wizard of the Ku Klux Klan and as the founder of the National Association for the Advancement of White People. He was an unabashed white supremacist and admirer of Hitler who peddled Nazi propaganda from his legislative office.

Johnston defeated Duke, 54 percent to 43.5 percent. But the demographics of the electorate made it plain that Duke had captured a clear majority of the white vote — as he would the next year in losing the governor’s race to Edwin Edwards.

But of course, that was then. That particular “then” was less than 25 years ago. Given that citizens become eligible to vote at 18, and given the propensity of Louisianians to stay in Louisiana, it’s safe to say many tens of thousands of Duke voters remain in the Louisiana electorate.

The right of citizens to vote for whom they choose is a bedrock of our democracy. And perhaps those Duke voters have undergone a conversion experience and now regard candidates of all colors with a salutary lack of prejudice.

Or perhaps not.

Gregory Roberts is chief of The Advocate Washington bureau. His email address is groberts@theadvocate.com. Follow him on Twitter, @GregRobertsDC.