In other words, if your grandfather couldn't vote, neither can you.
, that's the complete opposite of the situation. It was: if your grandfather could
vote, then so could you.
But your confusion is understandable. Both the dictionary definition you provided and the link that Phoenix
supplied got it wrong too.
Grandfather clauses were not meant to disenfranchise blacks: they were meant to enfranchise poor whites
. The literacy, property, and/or poll tax requirements were all designed to exclude blacks. If those requirements had been applied uniformly to all eligible voters, however, they would have disenfranchised a large number of poor, illiterate whites as well. So the southern legislators devised the grandfather clause, which only aided whites (presumably no black citizen had a lineal forbear who could legally vote before 1867). As a result, grandfather clauses effectively enlarged
the franchise by allowing whites, who would otherwise have been disqualified by the literacy, property, and/or tax requirements, to vote.
So, contrary to what you may have read, grandfather clauses didn't disenfranchise blacks (that was accomplished through other means), they enfranchised whites.