There's a political storm brewing on Florida's Atlantic Coast, just outside of Jacksonville. A voter guide falsely purporting to show a slate of endorsements by the local Republican party hit mailboxes in St. John's County, sowing confusion just as the primary was about to kick off this month. The latest salvo in what many say is already an overheated election cycle, the incident has brought attention to an intra-party slugfest being waged inside the local GOP, amid a fight for the future of how -- and how fast -- development should proceed in the area around historic St. Augustine.

"I saw the card, and I'm like, this is a real issue," St. John's County GOP Chair Denver Cook told ABC News. "I was in shock. I'm dealing with one of probably the most flagrant frauds on voters -- the day before early voting. It became an instant train wreck."

On the eve of the first ballots being cast last Friday, as the mysterious mailers began spreading, Cook said his phone began blowing up with perplexed messages. According to Cook, the glossy handout had a thickness, color scheme and font like the official voter guides put out by the local Republican party in June. And though it purported to be the "official 2024 membership-approved endorsements" of the county Republican party, it had a very different list of candidates from the ones the party had announced support for.

The new mailers also lacked any legal disclaimers explaining who paid for them, Cook said. And in pictures of the envelope that one of the fake mailers came in, which were reviewed by ABC News, the postmark was dated Aug. 7 -- timed to arrive just in time for Aug. 10th's early voting.

Cook, who is also running for St. John's clerk of courts and comptroller, didn't know how widely the phony cards were sent, but one thing was clear: In this predominantly Republican area, whoever won the primary would likely be the victor in November. "That's why there's such a fight," Diane Scherff, president of local political action committee "Trump Club of St. John's County" said. "It is the battle for the soul of St John's County," said Scherff, whose PAC endorsed a list of candidates in the spring that bucks the local GOP's.

So, the urgent question: Where did this pamphlet come from?

"I never thought anyone would go that far in the dirty trick universe," Cook told ABC News. "When we're talking about tight races, any illegal mailer like this claiming to be from the county party could alter elections." Cook says he has asked law enforcement to investigate the fraudulent pamphlets -- and that he would pursue legal action against those responsible. "Whoever did this knows the rules," Cook said. "There's a level of sophistication to this that isn't cheap."

Florida's Republican party chairman, Evan Power, said in a statement that they "are taking this matter very seriously and are investigating." "No Florida voter should be misled by anonymous, phony groups pretending to speak for the GOP," Power said.

Long before the mailers appeared, the St. John's primary had already stirred up bad blood over the question of who truly champions Republican policies and principles. At issue: the speed of local land development in one of the nation's fastest-growing and most influential areas, awash in campaign cash and high-dollar real estate deals. Some local party Republicans criticize others for being in developers' pockets; the other Republicans say their opponents are faux-conservative and accuse them of being Democrats in GOP clothing.

"Our local party has been taken over by Democrats, and Republicans using Democrats help to take a shortcut," said Jamie Parham, vice chair of the St. John's GOP board of directors. "If they're MAGA, they should be supporting the people that Trump supports." Cook pushes back against jabs like that. "I am a Republican, I support President Trump's campaign, I have supported his past campaigns, and as chair of the St. John's County GOP I continue to fight for the platform of our party," he said.

While local party officials had thrown their weight behind a slate of candidates that included several challengers to the current incumbents, the Trump Club of St. John's mostly endorsed the incumbent candidates. Then Trump himself, in an early morning Truth Social post last week, endorsed three incumbent county commission members from the Trump Club's list. It was recognition that Scherff said she'd been seeking for years. "I was so happy, after all the work I've done," said Scherff. "I thought that would be all we needed." But the fake voter guides, printed with the official GOP banner, threw the race into turmoil: The guide's endorsements were nearly identical to the slate of candidates endorsed by groups like the Trump Club.

Scherff said the resulting controversy enveloped the race -- and that she had no idea where the bogus guides came from. "I wish I knew, because then I could say to people, stop blaming me," she said, worrying that the controversy has cast doubt on Trump's support and undermined any momentum her group had. "It's been taken away," she said. "As quick as I got it, it's gone."

On Saturday, the last day of early voting, Trump reiterated his support for the same candidates in another Truth Social post.

The back-and-forth has grown so contentious that at one point a sitting county commissioner faced criminal prosecution for raising the upcoming election at a meeting. Krista Joseph, the county commissioner for St. John's District 4, describes herself as an often-lone dissenting voice on the five-person governing body. "I'm definitely a thorn in their side. I've voted with them when I think it's right, but I don't look at this as winning and losing. I'm representing," Joseph said. "It's not that I'm anti-development; I'm anti what they're doing to develop."

Joseph is not up for reelection this year -- but last November, at a commissioners' board meeting, she wanted to remind everyone who was. Joseph told members of the public that if they're "sick of the traffic" and "overcrowding in schools" and if they're concerned that that "developers are controlling the boards," they had a choice coming up. "There's hope," Joseph said from the dais. "Less than nine months, we have an election."

Several commissioners whose seats would be up were sitting with Joseph as she spoke. In a 4-1 vote less than a month later, the board censured Joseph, led by two of the incumbents who would go on to seek reelection -- both of whom would be endorsed by the Trump Club, and Trump. Outside counsel decided Joseph had violated election law by speaking out during a meeting, and noted the matter could be referred to local prosecutors for possible criminal charges, according to court documents. After a monthslong legal battle, U.S. District Judge Harvey Schlesinger ruled in Joseph's favor, finding her First Amendment right to free speech was protected, even at a county meeting.

"Simply because a person is an elected official, such as a County Commissioner, this rightful freedom to speak out so as to inform the electorate cannot be restricted," Judge Schlesinger wrote in his July 10 decision granting a preliminary injunction. "The threatened prosecution is chilling Commissioner Joseph's political speech in the last months of the primary election when this speech is most meaningful."

"The local Republican party has been splitting off into different factions," explains incumbent commissioner Christian Whitehurst. Whitehurst, who has been endorsed for reelection by the Trump Club and the former president, said he wants to make sure local government can keep up with all the development. "It's virtually impossible to stop all the growth," Whitehurst said. "We have a lot of people moving into not just St. John's County but the state of Florida. Of course with the sharp increase in growth comes the challenge to keep up in terms of infrastructure and services."

His primary challenger, Ann-Marie Evans -- who was endorsed by the local GOP -- criticizes Whitehurst on her campaign website as overseeing "the most overdeveloped area" and "STILL approving new homes by the thousands." "I am not opposed to all growth; I am opposed to exponential growth that does not keep pace with the need for infrastructure," Evans' site says.

Whitehurst says characterizing him as in cahoots with developers is unfair. "We have voted to deny many projects," he said. Whitehurst said he does not know who was behind the fake voter guides, and condemned "any attempt to mislead anybody." Parham, of the St. John's GOP board, said it wouldn't make sense for the current officeholders to be involved. "It doesn't benefit the incumbents if they sent it, because then they're the bad guy for committing election fraud," he said.

But Parham also decries the official endorsements made by his own local party. "The Republican Party should not endorse candidates in the primary," Parham said. "As a voter, you should figure out which group you most identify with, and that should be your voter guide."

The disarray over the fake voter guide reflects broader discussions around electoral integrity and partisanship breaking down attempts at unity within the local GOP. The inquiry surrounding the bogus material continues to loom over St. John's County as voters prepare for what promises to be contentious primaries. With the political climate growing increasingly fraught, all eyes will be on how party affiliations and internal factionalism shape the outcomes of this tight race.