Despite photos to the contrary, Alexandra Kerry (search) contends the transparent dress she wore to the Cannes Film Festival (search) was actually quite conservative.

The problem, she told actor-turned-interviewer Ben Affleck (search) in the September issue of Harper's Bazaar, was that it "did not withstand the impact of 3,500 flashbulbs."

"Because of the dark world of the Internet, I'm told there are now entire Web pages dedicated to my breasts," the 30-year-old actress and filmmaker is quoted as saying. "You gotta love the Internet."

In an article written by Affleck, who is a strong supporter of Democratic candidate John Kerry (search), Alexandra and sister Vanessa, 27, talk about the rumor mill, their stepmother, and why they chose to shed their anonymity to join their father's presidential campaign.

Affleck was once rumored to be dating Vanessa — a tabloid tidbit they both deny.

"Which one of you two did I have an affair with?" Affleck jokes in the opening sentence of the article, recounting a phone interview with Alexandra.

"I think it was Vanessa," Alexandra deadpans. "Yes, it was. You and Vanessa had a long and passionate affair."

Vanessa, a Harvard medical school student, told of her father's attempts to tell her about the "birds and the bees" during her teenage years, saying that he turned "different shades of red." She said he takes time out from politics to offer her a shoulder to cry on.

"I broke up with a boyfriend a while ago, and I came home sobbing pathetically and Dad was so sweet," Vanessa said. "He just put his arms around me and held me and told me, 'It's okay. I know it's hard and it's rough now, but you will get past it.'"

Kerry and his first wife, Julia Thorne, were separated in 1982 and divorced in 1988.

Alexandra said her mom, who now lives in Montana, is "exceptionally cool, incredibly generous, present and very loving."

Vanessa said Thorne is "a huge supporter of my father's and really believes he would make an excellent president."

Both daughters strongly defended Teresa Heinz Kerry, whose campaign trail candor has drawn some criticism.

"She is outspoken and very intelligent, and she is well studied in the environment and languages and other cultures," Alexandra said. "It just seems strange that anyone would say something negative about her."

Vanessa said that her father and stepmother, who married in 1995, have "an unbelievable partnership." Heinz Kerry's first husband, GOP Sen. John Heinz III, died in a 1991 plane crash. They had three sons, two of whom have been active in their stepfather's campaign.