The campaign event, planned for Saturday, marks the former president's return to a traditionally conservative state in which he remains very popular.
But his decision to hold the rally in Waco - best known for an armed standoff 30 years ago - has raised eyebrows.
The 1993 tragedy is seen as a landmark event for the American far-right.
A city of about 140,000 people in the heart of Texas, Waco is celebrated these days as host to Baylor University, the Dr Pepper Museum and the home-improvement reality show Fixer Upper.
Three decades ago, however, it was where FBI agents, the US military and Texas law enforcement laid siege to a religious cult known as the Branch Davidians.
The small, insular Christian sect was led at the time by David Koresh, 33, an apocalyptic prophet who allegedly believed he was the only person who could interpret the Bible's true meaning.
Under Koresh, the Branch Davidians had stockpiled weapons in order to become an "Army of God".
Authorities intended to conduct a surprise daylight raid on 28 February 1993 and arrest Koresh, but what ensued was a 51-day standoff that left 76 people dead, including more than 20 children and four federal agents.