CHARLESTON, S.C. (WCBD)- With just days until Charleston voters choose their next mayor, the race’s two remaining candidates tussled onstage Thursday night as they looked to build momentum heading into the runoff election.

The one-hour debate, held at News 2 in Mount Pleasant, saw incumbent Mayor John Tecklenburg and challenger William Cogswell sparred over top issues facing the city including plans for major development projects, flooding, and traffic congestion, among others.

Here are three takeaways from the night:

Dark money accusations spill onto debate stage

The debate turned personal about halfway through as heated rhetoric and scathing allegations carried over from the campaign trail to the debate stage.

Heading into Thursday night, Cogswell and Tecklenburg had each taken aim at their opponent’s campaign tactics, often lobbing accusations of dark money and extremism at one another.

The controversy sparked after several third-party ads trying to paint Cogswell as a far-right candidate supported by Moms For Liberty, a controversial, self-described “parental rights” group, began airing on local television.

Cogswell accused Tecklenburg of hiding his involvement with the groups that paid for the ads, noting that each was tied to a South Carolina-based lawyer, Butch Bowers, who served on former President Donald Trump’s legal team.

“Tecklenburg, a longtime Democrat, is collaborating with not one but two dark money groups to lie about me and he’s doing it with Donald Trump’s lawyer in a juvenile attempt to cover his tracks,” Cogswell said during a Nov. 1 news conference outside City Hall.

Tecklenburg responded to those claims Thursday night by accusing Cogswell of trying to “flip the conversation.”

“It was really him that started using dark money funding in his campaign months ago,” he said as he pulled out a flyer paid for by super-PAC American Prosperity Alliance that he claims was being distributed by campaign workers.

“Where’s the money coming from?” Tecklenburg asked.

“It’s an organization that I’m not associated with whereas yours…they set up two LLCs to lie about me John,” Cogswell responded seconds later. “Words matter, John. They really do matter. You know how many threats we’ve gotten?”

Later, the pair sparred again over a comment Tecklenburg made claiming Cogswell is backed by Moms for Liberty.

“Moms for Liberty is not supporting me or endorsing me or helping me in any way shape or form and I have no connection to Moms for Liberty,” Cogswell responded. “He’s calling us an extremist when nothing could be further from the truth.”

“It’s real easy, William. All you would have to do is return their money and denounce them,” Tecklenburg responded.

“They haven’t given me any money,” Cogswell fired back, adding that Tecklenburg was trying to turn the race partisan.

Sea wall sparks controversy

Another surprisingly contentious moment in the evening came when Tecklenburg accused Cogswell of changing his position on the sea wall, a proposed eight-foot protective barrier on the peninsula that is slated to cost an estimated $1.1 billion.

“Now Mr. Cogswell is in favor of it [perimeter protection], but he doesn’t want to get the federal government to help him,” Tecklenburg said. “I hate to tell him, we need their help.”

“I’m a pragmatist, I don’t want to waste four years on something that is going to have a very difficult time getting approved because it only helps the peninsula,” Cogswell responded. He previously said he would put an elevated edge around the peninsula, but does not support the current plan due to its cost and scope.

Cogswell then jabbed back at Tecklenburg saying he was unsure how the mayor would “sell that to the residents of Johns Island, West Ashley, James Island, and Daniel Island,” arguing that it will make things “much, much worse” for those communities.

“Now, he’s saying he wants to do a wall but just not as high or maybe not as good as the one we would build together with the federal government,” Tecklenburg said, adding that Cogswell “doesn’t have an estimate for his plan.”

“You don’t even have a design for your plan,” Cogswell shot back. “You have no idea what you’re talking about.”

A focus on development

The night opened with a discussion on two of the biggest stalled development projects on the city’s docket right now — Sumar Street and Union Pier.

When asked by moderator Carolyn Murray to explain his vision for Sumar Street — a 2.5 acre property in West Ashley that has been vacant for more than a decade — Tecklenburg said that he envisions it “remarkable gathering place” for the community with an underground parking garage but noted that city council “choked over the price.”

In responding to the same question, Cogswell cited the projected cost of the development as “something big to choke on” and proposed combining the Sumar Street lot with a nearby 30-plus acre parcel.

On the issues of overdevelopment and outdated infrastructure, there was little disagreement between the candidates.

In a question regarding livability concerns on Johns Island, Tecklenburg said the city was “playing catch-up with infrastructure.”

“Development is years ahead of the public sector and infrastructure,” Cogswell agreed.

But, Cogswell attempted to position himself as the better candidate to tackle these issues by repeatedly highlighting his professional background as a real estate developer. He also suggested he had a clearer vision and more pro-active approach to development projects.

Tecklenburg, on the other hand, primarily focused on his administration’s accomplishments on transportation projects and affordable housing as evidence that he should continue as mayor.