“A lot of Republicans are happy because we had successful statewide candidates, but those races were very, very close, and we lost some races too, especially in South Florida,” said Mr. Curbelo, 38, who bucked his party by adopting moderate positions on environmental issues and immigration. “As for 2020, I’m really worried that it is going to get a lot worse before it gets better.”

It was only this weekend, almost two weeks after the election, that Florida’s two biggest races were determined, with Senator Bill Nelson, the Democratic incumbent, conceding to Republican Gov. Rick Scott on Sunday, and Andrew Gillum conceding the governor’s race to his G.O.P. rival, Ron DeSantis, the day before.

In the interim, Democrats pursued numerous lawsuits challenging the vote-counting process in the Senate race — though Mr. Nelson’s odds of overtaking Mr. Scott were always fairly low — while Republicans lobbed unfounded accusations of voter fraud at the Democrats. The bickering focused even greater scrutiny on an American election system that is straining under human and mechanical error.

The acrimony in Florida followed a contentious, weekslong fight over voter suppression in Georgia, where the Republican secretary of state was overseeing a governor’s race in which he was also a participant. Those battles may foreshadow what 2020 will look like in other closely contested states, especially ones with increasingly diverse populations where conservative-dominated legislatures have tried to put more restrictions on voting while stoking paranoia over stolen elections.

“If what’s going on now is transposed to a presidential election, it would tax our system in a way that is much greater than what happened in 2000,” said Edward Foley, a professor of election law at Ohio State University and one of the country’s pre-eminent scholars on recounts. “As much as there was fighting in 2000, the rhetoric did not get as caustic as what we’ve seen in Florida this year — the allegations of stealing and rigging.”