Democratic presidential candidate Bernie Sanders came out against Maricopa County Sheriff Joe Arpaio during an Arizona rally on March 17, calling his behavior "outrageous and unconscionable." (Reuters)

FLAGSTAFF, Ariz. — Democratic presidential hopeful Bernie Sanders on Thursday called a controversial Arizona sheriff a bully and accused him of engaging in "un-American and uncivilized" law enforcement tactics.

Sanders's comments at a campaign rally here were directed at long-serving Maricopa County Sheriff Joe Arpaio, who prides himself on being “America’s toughest sheriff” and operates an infamous “tent city” jail where inmates endure extreme outdoor heat.

Sanders’s appearance was part of a series of stops planned ahead of Tuesday’s primary in Arizona, which he hopes will help him regain traction in a Democratic nominating contest he is losing to Hillary Clinton.

Thursday night’s rally was held at a Navajo casino, and the senator from Vermont focused heavily on issues facing Native Americans as well as Latinos.

Arpaio, also known for aggressive enforcement of immigration laws, has endorsed Republican front-runner Donald Trump in the presidential race.

Sanders recounted for his audience, estimated at 2,800 people, a trip that his wife, Jane, took earlier this week to the “tent city” as part of a separate campaign swing through Arizona on behalf of her husband. Upon learning of Jane Sanders’s plans, Arpaio showed up and offered the candidate’s wife a tour, and she asked him a series of pointed questions about the jail and immigration enforcement.

Sanders told the crowd at the rally that Arpaio “kind of ambushed” his wife.

"She asked him about racial profiling and he didn't have an answer,” Sanders said. “She asked him about conditions in tent city and other abuses that he has perpetuated, and he didn't have an answer. You know what, he cannot have an answer because what he is doing is un-American and uncivilized."

"It's easy for bullies like Sheriff Arpaio to pick on people who have no power, but if I'm elected president, the president of the United States does have the power,” Sanders said. “Watch out, Joe!”

His crowd broke into chants of "Bernie! Bernie! Bernie!"

Sanders was introduced at the rally by Katherine Figueroa Bueno, a 12-year-old who said she saw television coverage of her undocumented parents being arrested by Arpaio when she was 9.

“If elected president, we are going to pass comprehensive immigration reform and a path toward citizenship, whether Mr. Arpaio likes it or not,” Sanders said shortly after taking stage.

Democratic presidential candidate Bernie Sanders campaigned in Arizona on March 17 ahead of their primary next week. "If we can bring out large turnouts, we're gonna win this thing," Sanders said to a packed venue. (Reuters)

He also vowed to address the “appalling levels of inequality and systematic injustice” faced by Native Americans.

And Sanders put in a plug for changing the name of Washington’s football team.

“Washington has a very good football team but it doesn’t have to be called the Redskins,” Sanders said.