Since there is a lot of uncertainty out there about the process -- in California all it takes to amend the constitution is a vote of 50% plus one.
The relevant passage:
CALIFORNIA CONSTITUTION
ARTICLE 18 AMENDING AND REVISING THE CONSTITUTION
SEC. 4. A proposed amendment or revision shall be submitted to the
electors and if approved by a majority of votes thereon takes effect
the day after the election unless the measure provides otherwise. If
provisions of 2 or more measures approved at the same election
conflict, those of the measure receiving the highest affirmative vote
shall prevail.
source: California State Constitution online