76% of the states have supported gay marriage. Is that the 75% is what you want to dicker with the constitution? Until we have more voters persuaded by our arguments and willing to support conservative candidates none of this really matters.
The courts are doing it anyway, so we can call a hail Mary pass or just wait for the currently inevitable.
I believe that of the 76% only around 12 states approved it by vote of the people or act of their legislatures. The remainder was the result of Judicial Action. Good example being the ultra conservative State of California where it was banned by vote of the people but imposed by the Courts.