Sunscreen surely would have been a good idea. But Betty Castor forgot, leaving her light-skinned shoulders exposed as she worked almost invisibly along the sidelines of a pee-wee football game in the full afternoon scorch of Florida summer.

Behind her, an aide wrestled open a big blue-and-white umbrella and moved into position alongside, determined to protect her from the rays. They eased slowly toward midfield -- a genteel procession for the former schoolteacher whom the woman at the refreshment table calls "Miss Castor."

The Democrat ran one of the biggest state education departments in the country. She ran the second-biggest university in the Southeast. She navigated three decades of often-treacherous Florida politics.

But something about this slightly built grandmother of 10, who complains that she needs to eat more to keep up her weight, inspires an urge to shield her from the harsher side of public life.

The race she and 16 others have embarked on to replace retiring Sen. Bob Graham (D-Fla.) has been so ferocious that it was still taking loud, dramatic turns up through the final hours before Tuesday's primary. The Democrats clashed over Castor's handling of a terrorism case at the University of South Florida. The Republicans savaged one another over morality.

The bile prompted an extraordinary reversal Monday when the St. Petersburg Times, one of the state's most influential newspapers, took the rare step of withdrawing its endorsement of Republican Mel R. Martinez, President Bush's former housing secretary.

The paper's stinging editorial chided Martinez for taking "his campaign into the gutter with hateful and dishonest attacks" against his leading opponent, Bill McCollum, a retired 10-term congressman. The paper switched its endorsement to McCollum and criticized Martinez's campaign for distributing a flier that called McCollum "the new darling of homosexual extremists" for supporting hate-crime legislation that had bipartisan approval.

Gov. Jeb Bush (R) had earlier intervened in the race as a kind of eleventh-hour peacemaker, persuading Martinez to pull advertisements three days before the primary that portrayed McCollum as a supporter of gay rights. Martinez's campaign also has painted McCollum as "anti-family" because the retired congressman supports expanding stem-cell research. McCollum had a healthy lead until recent weeks when Martinez, who was born in Cuba, overcame a lackluster start and pulled even in the polls.

The Democrats have not been upstaged when it comes to turmoil in the race -- one of five to replace retiring Democratic senators in the South, a rare cluster that Republicans hope to use to fortify their control of the Senate. Howard Dean, the erstwhile presidential candidate, and Graham have come to Castor's defense, in part, because her candidacy stands at the nexus of two modern political realities: post-Sept. 11 terrorism angst and the power of "527s," the independent groups whose attacks have played into campaigns from Congress to the presidency.

Castor, 63, sees parallels between the Swift boat veterans campaign that has questioned Democratic presidential candidate John F. Kerry's Vietnam War record and advertisements that have criticized her for not firing Sami al-Arian, a professor who was videotaped shouting "Death to Israel" and was investigated for alleged terrorism links while Castor was the University of South Florida president.

"I'm appalled," she said recently at her Tampa campaign headquarters. "It's not going to work -- most people are so offended."

Castor, a former elected state education commissioner, faces an experienced slate of opponents. U.S. Rep. Peter Deutsch (D-Fla.) and Alex Penelas, the mayor of Miami, have leveraged their South Florida bases to counter Castor's strength in the central Florida hub of Tampa, where she lives.

The bitterness in the Democratic race has focused on terrorism, a not entirely unpredictable tack in a state where at least 14 of the 19 Sept. 11 hijackers lived and trained. A group formed by a former Deutsch campaign finance manager launched ads attacking Castor's handling of al-Arian, who was indicted in 2003 -- four years after Castor left USF -- on charges of raising money for Middle Eastern terrorists.

Castor, who has said tenure rules stopped her from doing more than suspending al-Arian, created a predicament with her response. She insisted that she had not received "one iota" of evidence of wrongdoing. Newspapers soon reported that she had seen search warrant affidavits for al-Arian's home.

"Iota" has become the biggest -- the most embarrassing -- word in the campaign. Deutsch, an orthodox Jew who does not campaign during the Sabbath, aired ads highlighting Castor's "iota" misstep. As the anti-Castor ads ran across the state, Dean criticized Deutsch's tactics, and Graham urged candidates to avoid negative attacks.

But Castor did not necessarily take his advice, airing an ad quoting newspapers that described the six-term congressman as "ruthless and nasty." Her staff also has posted a photograph on the Internet of a smiling al-Arian with President Bush at a 2000 campaign appearance.

Castor held a 2-to-1 advantage over Deutsch, with Penelas registering in the single digits, in a St. Petersburg Times-Miami Herald poll released Sunday. Befitting her reputation as a less-than-frenetic campaigner, Castor kept a leisurely schedule over the weekend.

At her campaign headquarters, Castor's husband, Sam Bell, a lobbyist and former state legislator, strolled in while his wife was giving a short speech Saturday. Castor asked him whether he had been rounding up votes. "Eighteen holes' worth," he said.

With the sun still shining, Castor called it a day, saying she was heading home to go to bed early. She climbed into her convertible and drove off -- with the top up.

In a poll released Sunday, Democrat Betty Castor held a 2-to-1 lead in the race to be the Senate candidate.