Legislative enactments are not normally effective for 90 days after the close of the legislative session. The 90-day delay does not apply in the case of (1) emergency laws, (2) laws that appropriate money for the "support and maintenance" of state agencies and institutions and (3) laws that increase taxes and fees. The Arizona Constitution provides that those three kinds of laws become effective immediately when the Governor signs the law into effect. Proposition 100 would amend the Arizona Constitution to give the Legislature the option of designating other effective dates for these three kinds of laws beside the date the Governor signs them.
Source for Popular Vote data: Arizona Secretary of State. State of Arizona Official Canvass - General Election - November 5, 1996, Arizona Secretary of State (http://www.azsos.gov/sites/azsos.gov/files/canvass1996ge.pdf) (accessed 26 May 2015)