DeSantis, whose endorsement by President Donald Trump helped the former congressman coast to victory in the August GOP primary, lost his cool when McDermott asked him about his relationship with conservative author David Horowitz.
But, they repeatedly returned to personal attacks in the process, suggesting the race has turned into an all-out verbal brawl as the candidates enter the home stretch of an election that has drawn national attention as something of a proxy to larger political headwinds in America.
Throughout the campaign, DeSantis has decried Gillum's plan to raise the state's corporate tax rate 40 percent, in order to put a billion dollars into education and teacher salaries.
Corey maintains that Gillum hasn't reimbursed him for almost $1,000 in expenses related to the Costa Rica trip.
During his 30-minute stump speech Thursday, Gillum reminded the audience about his opponent's "monkey this up" comment, adding that there's been "a lot more of the same" throughout the race.
Since the opening days of the general election contest between Gillum and DeSantis, race has been a subtext, with DeSantis receiving criticism for his choice of words during an interview with Fox News.
Florida Democratic Party chairwoman Terrie Rizzo hit out at Mr DeSantis on Twitter. But on Tuesday, former friend and mayoral campaign treasurer Adam Corey publicly released more than 100 pages of emails and text messages that appear to contradict some of Gillum's defenses. On Thursday, Jackson said he had asked the ethics commission to include the Tampa trip in his complaint.
The facts have been trickling in since the Federal Bureau of Investigation went public with investigative records, and once backed into a corner, Gillum resorts to whipping the race card from his slick suit jacket.
The latest records reveal the undercover agent, known as Mike Miller, likely paid a $4,386 food tab for a Gillum political committee fundraiser.
"That is what corruption is ..." McDermott pointed out that the former congressman had praised Horowitz as someone who "shoots straight" and "tells the American people the truth".
DeSantis, moreover, painted his opponent as an extremist who signed a "radical manifesto" by a group called Dream Defenders, which favors ending investment in Israel and has been critical of police and USA foreign policy.
"It was my first glimpse of what it meant for a family to have to worry about what it meant to be safe and secure and have to worry about your own protection out of fear that maybe one of those missiles might land on your family", he said.
The sparring, to some extent, obscured stark differences on the issues. DeSantis defends them as a viable option for some parents.
DeSantis stuck to his guns. He said during the debate that he would have pushed for a "stronger bill" than one Gov. Rick Scott signed in the wake of the shooting at Marjory Stoneman Douglas High School in Broward County.
The candidates also differ on voting rights for felons. DeSantis said former prisoners who have committed serious crimes should have to prove themselves worthy before getting the vote back.
"The mayor was invited by Peter Leach to a meeting at his office to learn about some of the work he was doing to advance wrap-around social services in schools and housing developments", Gillum's chief of staff, Jamie Van Pelt, told the Tallahassee Democrat previous year.