He is Arizona’s most popular politician and arguably America’s toughest sheriff, but today Joe Arpaio faces his biggest challenge: a grand jury investigation that could cost him his office.

“It is not right for law enforcement to abuse its authority in this way,” said Paul Charlton, a former US Attorney now representing one of Arpaio’s legal targets. “If you find yourself living in a place where law enforcement investigates its enemies and accuses judges who rule against them of crimes, you are either living in a third world county or Maricopa country.”

The Maricopa County Sheriff’s Office is America’s fourth largest sheriff’s department. For 18 years is has been run by Joe Arpaio, a flamboyant former Las Vegas cop and DEA agent who turned a local law enforcement agency into a national headline machine.

Arpaio forced inmates to wear pink underwear, claiming the color ‘calmed’ them. He created the nation’s first female chain gang. He reduced inmate meals from three to two a day, claiming to serve the cheapest prisoner meal in the U.S. at just 15 cents each.

Arpaio eliminated coffee, salt and pepper from inmate meals and banned skin magazines from jail cells. Inmates’ TV choices: the Disney Channel and C-SPAN. He created a tent city to handle inmate overcrowding. Those who complained about the heat got this from Arpaio. “It’s 120 degrees in Iraq and the soldiers are living in tents and they didn’t commit any crimes, so shut your mouths.”

Arpaio declared war on illegal immigration, by using local deputies to enforce federal immigration crimes. Sweeps and targeted enforcement in Latino communities led to massive arrests but charges of racial profiling.

Often called the P.T. Barnum of  law enforcement, Arpaio’s actions are not without critics. And now his political opponents may have found an ear in Arizona’s newly appointed US Attorney, former chief of staff for then Governor and now Homeland Security director Janet Napolitano.

“You have other folks who have gone to Washington to get the federal government to interfere with constitutional officer of the State of Arizona who is enforcing the law – if that is not corruption, I don’t know what is,” says Arpaio supporter and state senator Russell Pearce.

The sheriff is accused of abusing his police powersand using his “Public Corruption Task Force” to go after political enemies and critics. Officials currently under investigation by the Sheriff include:

Phoenix Mayor Phil Gordon

Chairman of the Maricopa Board of Supervisors Don Stapley

Supervisor and the county’s leading Hispanic politician Mary Rose Wilcox

State Attorney General Terry Goddard

County Manager David Smith

Presiding Criminal Judge Gary Donahoe

“It is beyond the ken of reasonableness, it not consistent with our ideas of justice for law enforce to accuse judges of crimes when all they have done is rule against law enforcement,” says Charlton, who now represents Stapley.

But others see the grand jury probe as retribution and a way to get Arpaio to back off – not just the politically powerful and well connected but to stop his high profile and effective sweeps against illegal immigrants.

“I applaud what Joe is doing,” says Pearce. “It is about time someone has courage to stand up for America. Citizens have a constitutional right to expect those (immigration) laws to be enforced. The public is on his side.”

At least three witnesses have been called to testify on Wednesday. The Grand Jury, typically composed of 16 to 30 citizens, can hear the evidence for several weeks. If it believes there is sufficient evidence a crime has been committed, the panel can return an indictment. If not, the case is usually dismissed.