TAMPA — Buoyed by a last-minute flood of signatures, the group pushing to legalize medical marijuana in Florida says it now has enough petitions to force a vote in November.

Elections officials are scrambling to see if that is true.

"We have collected close to 900,000 and by Monday or Tuesday of next week, we should be close to 1 million,'' said Ben Pollara, campaign director for United for Care said Thursday. "We are going to make it.''

The initiative, largely bankrolled by Orlando attorney John Morgan, was in serious jeopardy in mid December, when it was hundreds of thousands of signatures short with only about a month left.

Then Morgan opened the money spigot — raising pay for professional petition gatherers from $1 a signature to as much as $4, hiring people from around the country to solicit signatures outside courthouses, restaurants, stores and post offices.

Organizers also reduced the lag time between securing a signature and delivering it to an elections office for verification from about a week to one or two days, Pollara said. They rented vans to deliver petitions directly, rather than relying on the post office or delivery services.

The campaign has probably spent $2.5 million to $3 million so far, Pollara said.

Now county elections offices face a backlog of signatures that must be verified by Feb. 1. The campaign began in August. Some officials said they have received as many petitions since Christmas as they had in all previous weeks combined.

Hillsborough County had received about 30,000 petitions through Dec. 22. Another 40,000 have come in since then. About half the staff is processing petitions, making sure each signer is a registered voter and their signature matches the one on file.

Pinellas County has received 72,728 petitions since August, including 38,864 that came in since Monday.

The Pasco County elections office had processed almost 12,000 petitions through last weekend, validating almost 10,000, said Tami Bentley, senior deputy for voter services.

Then on Monday, United for Care delivered 8,537 more petitions and another 7,420 on Thursday. With several workers on holiday vacation, Bentley estimates that the office faces an eight- or nine-day backlog.

"We have had to bring on temporary help,'' Bentley said. "Our regular staff would never be able to accomplish this.''

A proposed constitutional amendment needs 683,149 valid voter signatures to be placed on the November ballot. But the marijuana campaign hopes to collect at least 1,050,000, Pollara said. That's because the rejection rate is running 28 to 29 percent — fairly typical of referendum drives. Hillsborough has rejected 26 percent of the petitions it has evaluated; Pinellas, 21 percent; Miami-Dade, 35 percent.

Many signers turn out not to be registered voters. Some sign more than one petition. Some signatures don't match ones on voting rolls. Sometimes, elections workers cannot decipher the name or address.

United for Care hired PCI Consultants, a California firm, to run the signature-gathering campaign. Collectors are paid for each signature, even if an elections office eventually rejects it, Pollara said. But PCI runs spot-checks on petition batches before turning them in. If too many signatures look questionable, the entire batch is returned to the collector without payment. Many professional gatherers work multiple campaigns, and know a high rejection rate could put them out of work.

Signatures must be verified by Feb. 1, and elections offices can take up to 30 days to process a petition. In theory, that means that petitions delivered this week may not get processed.

But elections officials said they are committed to counting as many as petitions as possible over the next few weeks — even though they are swamped.

"Our policy is that we are going to turn these around quickly as we can,'' said Craig Latimer, Hillsborough supervisor of elections. "It is our legislative responsibility to take care of these.'' The turnaround time in Hillsborough is about two weeks, so any petitions that arrive in "the next two weeks ought to get counted,'' he said.

The Pasco elections office has never failed to process any ballot petition because time ran out, Bentley said.

"We are going to give it our best shot,'' she said. "Of course, if they dump 70,000 on us on Jan. 30, that is not going to happen.''

Orange County has received 57,886 total petitions, 30,278 of them since Dec. 23. "Realistically, I'm concerned about anything received after Jan. 17th making the Feb. 1 certification deadline, said Elections Supervisor Bill Cowles. Fourteen employees are now working full time on petition processing, including six temporary workers.

United for Care plans to continue statewide collections for one more week, Pollara said, then evaluate whether it needs more.

County elections officials "have been really great about this," he said. "Most are saying that anything we get in by the second week in January will be counted. And even after that, they are saying they will give it their best shot if need be.''

If approved at the polls by at least 60 percent of voters, the amendment would legalize marijuana as a medical treatment for users who have a doctor's approval. Marijuana would have to be sold through state-regulated dispensaries; personal cultivation would still be illegal.

Public opinion polls indicate that a strong majority of Floridians favor the measure.

Even if the campaign collects enough valid signatures, the November vote could be derailed by the Florida Supreme Court, which has yet to rule on whether the ballot language is legal. Florida Attorney General Pam Bondi has argued that the language is confusing and also violates a requirement that the measure be limited to a single subject.

Morgan's group suspended payments to signature gatherers for about a month in the fall, trying to avoid spending a lot if the court threw out the ballot. Hillsborough County records reflect that hiatus, with only 2,400 petitions submitted during October — compared to 15,470 submitted on Monday. Morgan said that putting the campaign on hold was a mistake that forced the all-out dash.

Stephen Nohlgren can be reached at nohlgren@tampabay.com.