State economists on Wednesday began the work of determining the economic impact of a proposed amendment that would require statewide voter referendums on new casino projects.

The initiative, sponsored by Orlando-based Voters in Charge, could appear on Florida's 2018 ballot if supporters can collect nearly 700,000 signed petitions. The group already has 100,000 petitions, triggering the economic assessment.

Because mandatory referendums could result in the rejection of the destination resort casinos gaming companies are seeking to build in Florida, the tax revenue the casinos could generate wouldn't materialize. However, such votes could protect lucrative exclusivity agreements between the state and the Seminole Tribe, which runs Las Vegas-style card games at its Florida casinos and until recently had a compact with the state that guaranteed hundreds of millions of dollars in payments to Tallahassee.

Further complicating the economic forecast is the state's position as a destination in and of itself.

"Florida's always unique because we have tourists," said chief legislative economist Amy Baker. "We're a tourist destination, so we're kind of in hyper drive for anything that happens elsewhere, if you bring it into Florida."

While gaming executives have predicted a wave of new tourists if the resort casinos are built, critics warn of a cannibalization of the state's existing tourism industry. The costs of that, they argue, should be accounted for in the assessment of the proposed amendment.

"What we have seen time and time again with gambling is that the revenue figures and the jobs figures are exaggerated, and the social costs are much greater," said Voters in Charge Chairman John Sowinski. "We think that's why this is a decision that ultimately belongs with voters, not with the politicians."