The stakes are getting higher - politically and financially - in Florida’s heated campaign over a November referendum to allow doctors to prescribe marijuana.

The latest financial reports by the two main groups fighting the legalization of medical marijuana show a total of more than $7.7 million has been raised to oppose the constitutional amendment on the Nov. 4 ballot.

Proponents of the referendum got a head start with Orlando personal injury attorney John Morgan providing most of the $5 million spent so far by People United for Medical Marijuana, though much of that was devoted to gathering and validating voter petitions and defending the ballot language in court.

Deep-pocketed Republicans have since jumped into the battle. The Drug Free Florida campaign, which opposes the amendment, has raised $2.7 million, including a $2.5 million contribution from Las Vegas casino magnate Sheldon Adelson, a major Republican donor.

This week, the non-partisan Florida Sheriffs Association began a separate “educational campaign” against the amendment.

Polls show a majority of Floridians support medical marijuana legalization but constitutional amendments need a 60 percent majority in order to pass.

“I’m not 100 percent sure it’s a slam dunk,” said University of South Florida political science professor Susan MacManus. “We’re starting to see a lot more attention to some of the unintended consequences (of marijuana legalization) that have happened in Colorado, the negative side of it.”

The Florida amendment is also enmeshed in the hot race for governor. Republican Governor Rick Scott opposes it, while former Governor Charlie Crist, who is seeking to return to the office as a Democrat, supports it.

MacManus said constitutional amendment campaigns sometimes draw big money - trial lawyers and doctors have had big ballot battles over medical malpractice, and casino interests bankrolled some failed initiatives - but the marijuana fight figures to cost more than any previous issues election.

Florida congresswoman Debbie Wasserman Schultz recently said the amendment is too broadly drafted, prompting a stinging rebuke from Morgan, a major party donor who called for her removal as chairwoman of the Democratic National Committee.

The Florida legislature last month passed a bill that would legalize but strictly limit the distribution of a noneuphoric strain of marijuana believed to reduce epileptic seizures. Scott has said he will sign it into law.

November’s referendum is a broader proposal that would allow physicians to recommend the regular form of marijuana to people with debilitating ailments.