In Missouri, the partisan R base is larger than the partisan D base. If there's a significant moderate candidate in the race, it helps Republicans.
I mean considering a good chunk of the D base in MO is Black voters and white liberals in both majour cities and Columbia, I’m not so sure how true this is. Most stereotypical “swingy white suburbs” lean right in the state, plus Springfield. There is also still some ancestral Dem support in rural communities though idk if you’d call these “swing voters”.
Furthermore, we have seen some recent cases of Dems dramatically outperforming Trump statewide with not any significant cases on the GOPs side despite Trump supposedly turning off moderate/swing voters