Uh, a gathering that sends proposed amendments to state legislatures <i>is</i> a Constitutional convention. (And the first Constitutional convention was gathered to do just that for the Articles of Confederation, it just ended up sending back a recommendation to trash the whole thing and start over. The concern that one called to do draft amendments for the Constitution might do likewise has <i>always</i> been one of the reasons people fear calling one, and have generally preferred running specific amendments through the Congress even when its difficult to calling a convention with direction to address a particular concern.)