"America is a republic, not a democracy" has long been a popular meme on the right. AFAIK, the definitive history of that claim's origins and deployment in US political culture remains to be written. Here's one such usage I just encountered in this book. amazon.com/Mothers-Massiv…
The Smith v. Allwright decision (1944) had outlawed Mississippi's all white primary. The state faced the possibility of federal oversight of their elections to ensure fairness. The SCOTUS ruling had asserted that the "United States is a constitutional Democracy." But...
Staunch defender of Jim Crow and *former suffragist* Nellie Nugent Somerville, writing in the Jackson Daily News, argued that SCOTUS was wrong...the US was a republic, not a democracy.
Somerville: "From the earliest times in this republic the exercise of the election franchise has been protected by qualifications and restrictions." Here we see the "it's a republic, not a democracy" line being put to use to justify denying black people the vote in MS.
These paragraphs based on a 1974 thesis about Somerville succinctly capture how Southerners made sense of her transition from an advocating the expansion of the vote (to women) to restricting the vote (to black people.) It's all about staving off intrusive federal meddling. 
"A product of her culture" is doing a lot of work here, needless to say.
One final thing worth mentioning. Somerville died in 1952 at a hospital in the small town of Ruleville, MS. Ruleville was the hometown of Fannie Lou Hamer, a working class African-American woman who worked tirelessly to undo the antidemocratic work of people like Somerville.
There's now a statue commemorating Hamer in Ruleville. We need more such reminders on our national landscape that the best of us have long struggled to make the US a better democracy. And the struggle continues. civilrightstrail.com/attraction/fan…
Several years ago I researched how people used the term "democracy" in the 18th century. Here's what I found. tl;dr, The founders did indeed call America a republic. The central question they wrestled with was how democratic that republic should be. medium.com/@sethcotlar/ye…
The footnoted version of that appears in this book, along with many other smart meditations on the question of what people meant when the used the word "democracy" between 1750 and 1850. amazon.com/Re-imagining-D…
Saying something is a republic "not" a democracy, is like saying "this is a restaurant, not a source of nutrition." All restaurants are sources of nutrition to one degree or another, the question is how nutritious are they?
