provided, however, that, in the event that a special primary or special election to fill a federal or state office on a date other than the dates provided in this paragraph has been scheduled and it is possible to hold a special primary or special election to fill a vacancy in a county, municipal, or school board office in conjunction with such special primary or special election to fill a federal or state office, the special primary or special election to fill such county, municipal, or school board office may be held on the date of and in conjunction with such special primary or special election to fill such federal or state office, provided all other provisions of law regarding such primaries and elections are met.
OCGA § 21-2-540