It's entirely unnecessary for it to be a party position. Anti-GMO is an extremely widely held belief on the left.
"There's also a political difference. Republicans divide evenly on whether genetically modified foods are safe or unsafe. Independents rate them unsafe by a 20-point margin; Democrats, by a 26-point margin."
https://abcnews.go.com/Technology/story?id=97567&page=1
"Republicans are more skeptical of the theory of evolution, though by a surprisingly slim margin with 39 percent of them rejecting it as compared to 30 percent of Democrats. When it comes to other scientific matters, the waters are even muddier. For instance, Democrats and Republicans believe in the false link between vaccines and autism at roughly equal levels."
"Only 45 percent of Democrats support expanding the use of nuclear energy, as compared to 62 percent of Republicans"
https://reason.com/blog/2016/07/15/are-republicans-or-democr...
"The poll also shows more Democrats (9 percent) and independents (10 percent) say the measles vaccine isn't safe than Republicans who say the same (5 percent)."
https://www.washingtonpost.com/news/the-fix/wp/2015/02/09/he...