Maricopa County Sheriff Joe Arpaio has made a name for himself as a birther and an immigration hardliner. A new ad from his Democratic opponent, Paul Penzone, goes at him for something else: his office's mishandling of 400 sex crimes.

In the ad, which was posted to YouTube on Tuesday, features a child's voice talking about being sexually abused by her uncle, which the ad says is based on a real story.

"Mommy told me there were a lot of kids like me that Sheriff Joe didn't help," the voiceover says. "He says he's tough on crime, but I don't believe him. My uncle could come back."

Arpaio minimally investigated or ignored more than 400 sex crimes, including dozens of reports of child molestations, in the three years leading up to 2007, the Associated Press reported in December. East Valley Tribune won a Pulitzer for a 2008 investigation of the sheriff's office's handling of criminal investigations, also finding that many sexual assault cases were ignored.

"Children are our most precious assets," says Penzone, a longtime law enforcement officer. "This will never be tolerated under my watch."

Penzone spoke to The Huffington Post earlier this year, emphasizing his concern that the sheriff is spending his time on the wrong things -- illegal immigration, for example -- instead of keeping his focus on dangerous criminals. Although Arpaio has been popular, he said the tide may be turning on the sheriff. A poll released last week by progressive group Citizens for a Better Arizona found that Arpaio's approval rating fell to 53 percent, and 65 percent of those polled disapprove of his investigation of President Barack Obama's birth certificate.

"People are more aware of what's occurring behind the scenes as opposed to what's occurring on TV," Penzone said then. "Over time, much like a bad relationship, you realize it's unhealthy."

Watch the ad:

Also on HuffPost:

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  • Maricopa County Employees Call Latinos Derogatory Names

    Jail employees frequently refer to Latinos as "wetbacks," "Mexican bitches," and "stupid Mexicans," according to the lawsuit. An email that included a photography of a Chihahua dressed in swimming gear with the caption "A Rare Photo of a Mexican Navy Seal" was widely distributed by sheriff's office supervisors.

  • Officers Mistreat Latinos In Routine Traffic Enforcement

    The lawsuit recounts how a Latina woman who was five-months pregnant and a U.S. citizen was stopped as she pulled into the driveway. "After she exited her car, the officer then insisted that she sit on the hood of the car. When she refused, the officer grabbed her arms, puled them behind her back, and slammed her, stomach first, into the vehicle three times. He then dragged her to the patrol car and shoved her into the backseat," reads the complaint. She was cited for failure to provide identification, which was later changed to failure to provide proof of insurance. The issue was resolved when the woman proved she had insurance to a court. In yet another case, two officers followed a Latina U.S. citizen a quarter of a mile to her home without flashing their lights. When she arrived home, they insisted that she stay in the car. The reason for the stop was a "non-functioning license plate light." After she tried to enter her home, officers took her to the ground, kneed her in the back and handcuffed her. She was brought to a Maricopa County Sheriff's Office (MCSO) substation and cited for "disorderly conduct," which was later dismissed, according to the lawsuit.

  • Latinos Are Indiscriminately Detained In Immigration Raids

    A Latina born in the United States was taken into custody for four hours in a raid to determine her immigration status. Arpaio was quoted in response, "That's just normal police work. You sometimes take people in for probable cause for questioning and they're released." The suit notes that the reason for her detainment -- being Latina and present during a raid -- were insufficient.

  • Arpaio And MCSO Staff Foster Discrimination Against Latinos

    Arpaio received a letter reading, "If you have dark skin, then you have dark skin. Unfortunately, that is the look of the Mexican illegals who are here illegally. ... I'm begging you to come over ... and round them all up." The sheriff labeled this as "intelligence" and forwarded to his deputy chief of enforcement operations for someone to "handle this." Upon receiving a letter backing the policy of "stopping Mexicans to make sure they are legal," he sent a letter of appreciation to the authors and kept three copies for himself, according to the lawsuit. An email circulated among MCSO staff had an image of a fake driver's license from "Mexifornia" and listed the driver's class as "illegal alien."

  • MCSO Employees Fail To Provide Assistance To Prisoners With Limited English

    The failure to provide adequate language assistance caused some female Latina prisoners to remain with sheets or pants soiled from menstruation, alleges the suit. Others have allegedly been put in solitary confinement for "extended periods of time" for not understanding a command in English.

  • MCSO Arrests Arpaio Critics Expressing Their First Amendment Rights

    The suit claims on multiple occasions that people were arrested for merely applauding against the office's immigration policies. The judge presiding over the case of the arrestees found that the deputy who made the arrest "believes it is his role to make uncomfortable anyone who express[es] views that disagree with the sheriff" and that he had "trampled" over the First Amendment. The court acquitted them.