Due to its relative simplicity and ease of use, transient transfection of mammalian cell lines with nucleic acids has become a mainstay in biomedical research. While most widely used cell lines have robust protocols for transfection in adherent two-dimensional culture, these protocols often do not translate well to less-studied lines or those with atypical, hard-to-transfect morphologies. Using mouse pluripotent stem cells grown in 2i/LIF media, a widely used culture model for regenerative medicine, this method outlines an optimized, rapid reverse transfection protocol capable of achieving higher transfection efficiency. Leveraging this protocol, a three-plasmid poly-transfection is performed, taking advantage of the higher-than-normal efficiency in plasmid delivery to study an expanded range of plasmid stoichiometry. This reverse poly-transfection protocol allows for a one-pot experimental method, enabling users to optimize plasmid ratios in a single well, rather than across several co-transfections. By facilitating the rapid exploration of the effect of DNA stoichiometry on the overall function of delivered genetic circuits, this protocol minimizes the time and cost of embryonic stem cell transfection.