Lawyers are descending on Florida as the state braces once again to become ground zero in a national election fight, and the epicenter appears to be Broward County where late-arriving ballots in Democratic strongholds are fueling accusations of political shenanigans.

Florida Republican Sen. Marco Rubio has highlighted a range of possible problems in the county—including a suspected mystery truck delivery of ballots—and has criticized local officials for their molasses-like process of counting ballots in the Senate race between Republican Rick Scott and incumbent Democratic Sen. Bill Nelson.

Scott, Florida’s outgoing Republican governor, warned of possibly “rampant fraud,” and filed lawsuits late Thursday against the top election officials in two heavily Democratic counties as they continue to report new votes.

“Under #Florida law, county must upload by 7 p.m. day BEFORE election ALL early votes canvassed & tabulated by end of early voting & report results within 30 minutes of polls close. 60 hours after that deadline only 1 of 67 counties is still counting early votes, #BrowardCounty,” Rubio tweeted Friday morning.

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Minutes later, he added that early voting in Broward County had ended “108 hours ago,” and that county officials “won’t disclose how many ballots are left.”

“The incompetence & the violation of #Florida reporting requirements by #BrowardCounty elections dept could impact more than just the outcome. The last thing our already dangerously divided nation needs is an important election 1/2 our people believe was rigged by the other 1/2,” Rubio tweeted.

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Rubio also shared a video, allegedly showing ballots being transported in private vehicles from polling places.

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Further, Rubio shared the account of a lone box labeled “Provisional Ballot Box” left at a county elementary school that served as a polling precinct. But the reporter who originally flagged the abandoned box later walked it back, citing another local reporter who tweeted a photo showing the apparent container filled with little more than supplies.

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In the Scott campaign’s lawsuit, joined by the National Republican Senatorial Committee (NRSC), they allege that officials in Broward County are hiding critical information about the number of votes cast and counted. In a parallel suit against Palm Beach County, Scott and the NRSC charge that the election supervisor there illegally used her own judgment to determine voter intent when reviewing damaged or incorrectly filled-out absentee ballots, while refusing to allow impartial witnesses to monitor the process.

"I will not stand idly by while unethical liberals try to steal an election," Scott said at a press conference outside the Governor's Mansion, as he slammed potential "rampant fraud" in the race.

On Thursday, a Nelson spokesperson tersely dismissed Scott's effort: “The goal here is to see that all the votes in Florida are counted and counted accurately. Rick Scott’s action appears to be politically motivated and borne out of desperation.”

Scott complained that the late-arriving votes were steadily shaving his lead.

"Late Tuesday night, our win was projected to be around 57,000 votes," Scott told reporters. "By Wednesday morning, that lead dropped to 38,000. By Wednesday evening, it was around 30,000. This morning, it was around 21,000. Now, it is 15,000."

He continued: "On election night, Broward County said there were 634,000 votes cast. At 1 a.m. today, there were 695,700 ballots cast on election day. At 2:30 p.m. today, the number was up to 707,223 ballots cast on Election Day. And we just learned, that the number has increased to 712,840 ballots cast on Election Day. In Palm Beach County, there are 15,000 new votes found since election night."

He specifically called out the counties' respective elections supervisors, Brenda Snipes and Susan Bucher.

Florida law requires a machine recount when candidates are within 0.5 percentage points of one another.

A mandatory recount now appears imminent, not only in Scott and Nelson’s race, but also in the agricultural commissioner contest and Florida’s high-profile gubernatorial battle between Democrat Andrew Gillum and Republican Ron DeSantis.

Gillum, who hoped to be the state’s first African American governor, conceded late Tuesday night. But by Friday, the Tallahassee mayor was reconsidering that concession, which is nonbinding.

"On Tuesday night, the Gillum for Governor campaign operated with the best information available about the number of outstanding ballots left to count," Gillum's campaign said in a statement Thursday evening. "Since that time, it has become clear there are many more uncounted ballots than was originally reported. Our campaign, along with our attorney Barry Richard, is monitoring the situation closely and is ready for any outcome, including a state-mandated recount."

Fox News' Gregg Re and Heather Lacy contributed to this report.