Mel R. Martinez was in his element, a gathering of Hispanic movers and shakers, many with immigrant success stories like his own. The perfect spot, in other words, to roll out a few pearls from his father, who followed him from Cuba to 1960s Florida.

"Politics is dirty," Martinez recalled his father telling him. "Don't get involved in politics."

The audience broke into peals of laughter, and even Martinez, a less-than-animated speaker prone to expressionless monotone, cracked a smile. The irony of the punch line was lost on no one.

Martinez, 57, a Republican who resigned as President Bush's secretary of housing and urban development in December to run for the seat of retiring Sen. Bob Graham (D), is locked in one of the fiercest political contests in the nation. The race -- beginning with the party primaries and stretching into a general election pitting Martinez against Democrat Betty Castor -- has been dominated by attacks and counterattacks, stinging slurs and tepid apologies.

Both parties have engaged in the mudslinging, but the tenor of Martinez's attacks has drawn the most attention and the most disdain. Before the Senate race, Martinez was defined by his amiable nature and likable ways, but those days are gone.

During the primary, Martinez's campaign called former representative Bill McCollum (R-Fla.) -- who had been considered one of the more conservative voices in Congress -- "the new darling of homosexual extremists" because he supported hate-crime laws and "anti-family" for favoring advanced stem cell research.

Martinez has angered police unions by referring to federal agents involved in the case of Elian Gonzalez, the Cuban boy whose tangled custody and immigration case became a national cause celebre in 2000, as "armed thugs." Martinez has accused Castor of allowing a "terrorist cell" to fester on campus while she was president of the University of South Florida.

Martinez's staff scheduled, then canceled two interviews for this article, and has not returned phone calls to schedule another interview.

The state's big newspapers have been nearly unanimous in their sense of disapproval of Martinez. Orlando Sentinel columnist Myriam Marquez wrote that Martinez's supporters "must wonder what caused Mr. Nice Guy to turn into a Mel Vicious." Novelist Carl Hiaasen said in his Miami Herald column that Martinez had "morphed into a nasty right-wing drooler." The St. Petersburg Times took the rare step of withdrawing its recommendation of Martinez one day before the primary, saying he had taken "his campaign into the gutter with hateful and dishonest attacks."

The cumulative effect of these criticisms, and others, is still being assessed. Certainly, Martinez, who has basked in support from the White House, appeared to suffer few ill effects during the primary, which he won by a comfortable margin after a late-surge in the polls erased memories of his lackluster start. But recently, Martinez's lead in the race against Castor has vanished, with the Democrat pulling even in polls conducted shortly before their first debate on Monday.

The central theme of the testy debate, just as it has been during the race, was Castor's handling of a professor who was investigated for terrorism links in the mid-1990s while she headed the University of South Florida. Federal agents revealed to Castor that they were investigating professor Sami al-Arian, who was captured on tape chanting "Death to America, death to Israel," for terrorist links. She has said tenure rules prevented her from doing more than placing al-Arian on paid administrative leave, which she eventually canceled after reinstating him and closing a center he operated that was suspected of terrorist ties.

Martinez accuses Castor, who left the USF five years ago, of not acting aggressively. He has aired television ads saying, "Islamic Jihad used her university as cover." Islamic Jihad is shorthand for Palestinian Islamic Jihad, the terrorist group of which al-Arian has been accused of being a top leader.

One Martinez ad features former Immigration and Naturalization Service agent William West, who investigated al-Arian, saying Castor's "lack of strong leadership allowed a dangerous situation to get worse." Shortly after the ad began running, the Martinez camp found itself responding to revelations that West was also one of the agents -- to whom the campaign had referred as "armed thugs" -- involved in the Elian Gonzalez case.

Martinez has said the armed thug comment was "inappropriate" and blamed his staff.

Castor has attempted to fend off Martinez's criticisms of her handling of al-Arian, who is in federal prison awaiting a January trial after being indicted last year on charges of raising money for terrorist groups, with negative ads of her own. One of her first ads in the general election highlighted a photograph of al-Arian with then-presidential candidate George W. Bush at a 2000 campaign appearance. Castor's allies have delighted in reminding reporters that Bush referred to al-Arian's son as "Big Dude" at the event. The ad also notes that al-Arian attended a meeting on faith-based initiatives at the White House in 2001 with Bush adviser Karl Rove.

Beyond the al-Arian case, neither side has succeeded in lifting another issue to the fore in the campaign. Martinez stresses his immigrant's tale: leaving Cuba at age 15, thanks to a Catholic resettlement effort known as "Pedro Pan," living in foster homes, becoming a successful trial lawyer, a well-liked local politician in Orlando and housing secretary. Castor leans on her widely praised leadership of USF and her tenure as the state education secretary.

They have stark differences on policies. Castor said during the debate that she favors a minimum-wage increase because 400,000 Floridians, including "many women and Hispanics," work for the minimum wage; Martinez prefers an emphasis on job training, saying that a minimum-wage increase would be "illusory," because "a buck an hour is not going to bring someone out of poverty." Martinez said he would still vote for the war in Iraq, even though no weapons of mass destruction have been found; Castor said she would not.

They even disagreed about negative campaigning. Castor said she would stop if Martinez would. Martinez responded: "I'm not going to make a strategy for my campaign here under these lights."

Republican Mel R. Martinez, above, is vying for the seat of retiring Sen. Bob Graham (D-Fla.).