Our theory predicts that for a proton coupled electron transfer model system (Shin-Metiu model ), the ground state barrier height can be modified through light-matter interactions when the cavity frequency is in the electronic excitation range. This novel change in the ground-state chemical reactivity is achieved through electronic strong coupling as opposed to the more common use of vibrational strong coupling for modifying the ground state. Our simple theory explains several recent computational investigations that discovered the same effect. We further demonstrate that under the deep strong coupling limit of the light and matter, the polaritonic ground and first excited eigenstates become the Mulliken-Hush dia-batic states, which are the eigenstates of the dipole operator. This work provides a simple but powerful theoretical framework to understand how strong coupling between molecule and cavity can modify ground state reactivities.