Because 85% of the morons who will promote this amendment won't be able to keep their big traps shut about the sodomy decision when talking about this. They will drone on about it, over and over and over - the soundbites will take over every other agenda.
In the end, many will wonder what the purpose of government is, why the GOP has so many red faced, middle aged, pissed off white guys dominating the agenda, and that incredible number of swing voters will swing right over to the D column.