Joe Arpaio, the 84-year-old Sheriff of Maricopa County, Arizona, and a controversial opponent of undocumented immigration, said that "my most important mission is to elect Donald Trump," citing his willingness to build a wall and secure American borders.
Arpaio, who walked onto the stage at the convention to resounding applause, has been a lightning rod for scandal since his election in 1993, largely because of his staunch policies, which many view as anti-immigrant.
"We are more concerned with the rights of illegal immigrants than we are the citizens of our own country," he said.
He also spoke of the importance of respecting police in the wake of the murder of police officers in Dallas, Texas, and Baton Rouge, Louisiana this month.
"Now more than ever we must have respect for the police," he said. "The highest levels of government must have our back."
The crowd chanted "build a wall" during his speech, referring to Trump's promise to build a wall along the Mexican border to slow the path of would-be illegal immigrants.
As a Sheriff, Arpaio established a "tent-city" as an extension to Maricopa County jail in 1993 that houses many illegal immigrants. Arpaio once jokingly referred to the complex as a "concentration camp," and Amnesty International, as well as other human rights organizations, have condemned the facility as inhumane.
He became a known figure on the national stage after challenging the authenticity of Barack Obama's birth certificate, a point of view that he shared at that time with Donald Trump. Arpaio has been closely allied with Trump throughout his rise to the top of the Republican ticket, and relished the opportunity to provide security to Trump at his rallies.
Arpaio has also been criticized for failing to investigate several sex crimes, including cases of child rape.
The sheriff has conceded investigative failures in his special-victims unit regarding sex crimes, and said that it was not uncommon for police agencies to struggle with such matters, according to the Arizona Republic. He said that he believed that his agency he was being singled out, the paper said.
Arpaio has been accused of racial profiling, and abuse of power at times in his career, but he has also won fans among hard line conservatives, nationalists and other people concerned about undocumented immigration for his perceived toughness in enforcing border laws.
His attorneys have fiercely denied all allegations of racial profiling, according to the Arizona Republic.
This week, a judge presiding over a racial profiling case against Arpaio handed down punishments against the octogenarian lawman for his decision to prolong immigration patrols months after he was told to stop them.
U.S. District Judge Murray Snow ordered an overhaul of internal affairs investigations at the Maricopa County Sheriff's Office after previously finding Arpaio in civil contempt of court for disobeying him, according to the the Associated Press.
Additional penalties are expected, the report said.