The Governor and Lieutenant Governor shall be elected for the term of four years by the qualified voters of the State. They shall be elected jointly by the casting by each voter of a single vote applicable to both offices, as shall be provided by law. The slate of candidates having the highest number of votes cast jointly for them for Governor and Lieutenant Governor shall be elected; but if two or more slates of candidates shall be equal and highest in votes, the election shall be determined by lot in such manner as the General Assembly may direct.