DAVIE, Fla. -

Florida's U.S. Senate contenders took a break from their incendiary television ad war to meet face to face in their only scheduled debate Wednesday night, a one-hour affair at Nova Southeastern University.

Two-term Democratic incumbent Sen. Bill Nelson faces a Republican challenge from U.S.Rep. Connie Mack IV of Ft. Myers in a race that will help determine control of the U.S. Senate.

Republicans need to pick up three seats and the presidency to gain control of the chamber. They would need a net gain of four seats if President Obama wins election.

Mack won the primary over a weak field of Republican candidates and declined to debate any of them.

Now, with Nelson holding a thin but significant lead in most polls, it is Mack accusing Nelson of ducking more debates.

Both camps had agreed to two televised debates, but Mack took issue with one of the debates' co-sponsors and pulled out. By the time a new sponsor surfaced, Nelson's camp said it was too late to restart the debate negotiation and planning process.

With no other face to face meetings held or planned, most Floridians may be basing their impressions of the candidates on a slew of negative ads launched by the campaigns and the surrogates.

Nelson tried to define Mack early on as an entitled, hard-partying scion of the man he replaced in the Senate, Connie Mack III, noting the younger Mack was a promoter for the Hooters restaurant chain and had been charged years ago in a bar brawl.

A Super PAC supporting Mack repeatedly broadcast an ad accusing Nelson of taking advantage of an agricultural tax exemption on land he later sold for a large profit. Speaking over images of cartoonish cows, the narrator accused Nelson of "milking the system."

Moderator Michael Williams, an anchor for WPTV in West Palm Beach, oversaw a panel of three journalists from across the state, who were to ask questions about the economy, foreign affairs, healthcare and entitlements, among other subjects.

Nearly 500 people can fit in the auditorium, with tickets provided to each campaign and party, as well as debate sponsors and the host university.