“Nasty is the new normal in Florida,” said Dan Gelber, a former state senator and Democratic leader in the State Capitol who is not inclined to shirk from the state’s political tussles. “Politics here is very gutterlike. It’s like a very bad reality TV show that still gets very high ratings.”

Because elections are so tight and a small number of votes can decide races, each voter is highly coveted and doggedly targeted.

“It’s a true swing state, and a close state ignites people’s passions,” said Roger Stone, a longtime Republican consultant who lives in Miami Beach. Add to that the state’s mix of immigrants, many from countries well practiced in tainted politics, and New Yorkers, who are accustomed to delighting in political rumbles, and the result is not altogether unpredictable.

Nowhere is this more obvious than in South Florida.

Since he was elected to Congress in 2010, Mr. Rivera, one of three Republican Cuban-American House members from Miami, has been dogged by allegations of wrongdoing while he was a state legislator. On Wednesday he was charged by the Florida Commission on Ethics with 11 counts of filing fraudulent financial disclosure forms, misusing campaign funds and concealing a $1 million consulting contract with a Miami gambling business while he served in the State House.

Mr. Rivera, who was Senator Marco Rubio’s roommate when both were state representatives, called the charges false in a statement, but he is also confronting another series of damaging accusations.