PHOENIX - It's believed to be the first attack ad ever on Joe Arpaio by one of his opponents running for sheriff.
The commercial from Democrat Paul Penzone hits the airwaves Thursday on TV stations across the Valley.
Penzone hasn't even won the Democratic primary for Maricopa Count Sheriff yet, but in the ad, Penzone sets his sights on his would-be opponent in the general election, Sheriff Joe Arpaio.
"I remember when the sheriff came on to talk about this birther investigation and thought how ridiculous is this," Penzone says in the ad.
The ad attacks Arpaio for his investigation of President Obama's birth certificate.
"We know that it was politically motivated, our sheriff recognizes it's a polarizing issue," Penzone goes on to say in the commercial.
A spokesperson for Arpaio wouldn't address the specific claims in Penzone's ad.
But his lead investigator Mike Zullo, during an appearance on ABC15 Wednesday morning, denied any allegation politics played a role.
When asked by ABC15's Connie Colla if Zullo conducted the investigation for political reasons, Zullo responded "no."
In the TV commercial, Penzone goes on to attack the Sheriff's birther investigation as having no public safety value for residents of Maricopa County.
"This is a gimmick," Penzone says in the spot.
However, in Tuesday's news conference, Arpaio defended the investigation.
"This is an official investigation zeroing in on possible fraud of government documents," said Arpaio.
A spokesperson for Arpaio's campaign declined further comment saying "Penzone is not even the Democratic nominee."
The spot will begin airing Thursday, the same day the racial profiling lawsuit gets underway accusing Arpaio of harassing and discriminating against Latinos.
A Penzone spokesperson says that's no coincidence.