Yes, this confused me, too. This is what I found. Basically, the Supreme Court invalidated part of our constitution, the gov convened a commission to see if we needed a convention, they came back with recommendations for one, voters got to vote on a referendum to have one and passed that, the convention happened, but then the voters did not approve the new constitution.
Here are some snips from some sources I found:
“Maryland's constitutional provision on apportionment was invalidated by the U.S. Supreme Court in 1964. By executive order on June 16, 1965, Governor J. Millard Tawes created the Constitutional Convention Commission, chaired by H. Vernon Eney, to study the need for constitutional revision.”
“The commission was divided into ten committees, including convention procedures, elective franchise, finance and taxation, local legislation, and the executive, legislative, and judicial branches. The commission and its committees prepared the specific recommendations requested by the governor and incorporated them into a draft constitution. The commission held its last formal meeting in December 1966, published its interim report on 26 May 1967 and its final report on 25 August 1967, and then disbanded. Acting on the recommendations of the commission that the present constitution required revision and that a convention should be called, the General Assembly enacted legislation to that effect in 1966 (Chapter 500, Acts of 1966). In a referendum held on 13 September 1966 to determine whether Marylanders wanted a convention, the electorate voted overwhelmingly in favor of a convention. “
“In a referendum held on 14 May 1968, the constitution failed ratification. “
So it sounds as if it had nothing to do with the 20-year question.
I guess they still had to ask the question again 2 years later?