An amendment convention could be called with how many of the states sending delegates to debate the need for amending the constitution?

Article V describes the process necessary to reform the constitution. It establishes two methods of proposing amendments: by Congress or by a national convention requested by the states. With the first method, Congress can propose an amendment with the votes of two thirds (of a quorum, not necessarily of the entire chamber) of the Senate and the House of Representatives. With the second method, the legislative bodies of two thirds of the states can convene and force Congress to convene a national convention, and Congress must convene that convention in order to consider the proposed amendments. Until 2015, only the first method has been used - proposed by Congress.

Once proposed - either by Congress or by national conventions - the amendments must be ratified by three-fourths of the states for them to take effect. Article V gives Congress the option of requiring ratification by the legislative bodies of the states or by special conventions convened in the states. The ratification method by convention has only been used once (to approve the Twenty-First Amendment). Article five currently only imposes a limitation on the power of amendment - no amendment can deprive a state of its equal representation in the Senate without the consent of that state.