FORT MYERS, Fla. — Senator Marco Rubio went down the list of political enemies and rivals like a roll-call vote: President Obama. Hillary Clinton (“more Obama”). Both of his possible Democratic rivals, Representatives Patrick Murphy (“he has not had to struggle a single day in his life”) and Alan Grayson (“who frankly I don’t think is well”). And even Senator Chuck Schumer, Democrat of New York, whom Mr. Rubio says he wants to prevent from becoming majority leader.

The name that did not cross Mr. Rubio’s lips as he addressed supporters at the opening of a new campaign office here was Carlos Beruff, a wealthy businessman and Mr. Rubio’s lone, long-shot Republican challenger in Florida’s primary on Tuesday. Mr. Beruff’s central campaign theme seemed to be that Mr. Rubio was insufficiently fond of Donald J. Trump.

Mr. Rubio began this year with hopes of being the face of generational change in his party on the road to the White House. Instead, he found himself reversing a decision to leave the Senate, seeking a second term for a job that he had essentially scorned.

But Mr. Rubio’s race is only one in a slew of portentous and, in some cases, downright wacky contests that have dominated the state this year. Last year, acting on a Florida Supreme Court ruling that the congressional district map was unconstitutional, the court upheld a new map recommendation that altered 24 of the state’s 27 congressional districts.