(CNN) The big rumor -- emphasis on the word "rumor" -- ahead of President Donald Trump's trip to Phoenix for a campaign rally tonight is that he might issue a pardon for Joe Arpaio, the controversial former sheriff of Maricopa County.

"I am seriously considering a pardon for Sheriff Arpaio," Trump told "Fox News Sunday" earlier this month . "He has done a lot in the fight against illegal immigration. He's a great American patriot, and I hate to see what has happened to him." Trump later retweeted the article about his comments.

The "will he/won't he" speculation will run all day -- right up until Trump takes the stage in Phoenix around 10 p.m. eastern tonight. So, it's worth asking: How did we get here with Joe Arpaio?

Arpaio first came to national prominence in the early 1990s when, as newly elected sheriff of Maricopa County, he pushed the construction of Tent City -- an open-air jail he viewed as not only a solution to prison overcrowding but also a way to burnish his tough-on-crime persona.

"We're going to do it, and it's time to get tough around here," Arpaio said in 1993 when Tent City was unveiled, according to the Arizona Republic . "And to get tough, you have to have a place to put the bad guys."

Arpaio also made prisoners wear pink underwear and pink handcuffs as a way of shaming them (and to stop them from stealing each others' clothes). In the mid-1990s, he reinstated chain gangs -- including for women and juveniles. He pushed for every mug shot to be posted online. He cut down prison meals to two a day -- no lunch! -- and banned the use of salt and pepper to save money.

Arpaio's reputation -- which he proudly embraced -- as "America's Toughest Sheriff" made him a coveted endorser as Republicans more aggressively embraced hard-line immigration policies over the past decade.

It was right around that same time -- in May 2013 -- that the Justice Department announced a lawsuit against Arpaio alleging a long-standing record of discrimination against Latino citizens by his office. That suit alleged the Maricopa County Sheriff's Office had targeted Hispanic immigrants during patrols and traffic stops and had violated Hispanics' right to privacy. It was eventually settled in 2015

Arpaio's relationship with Trump began earlier this decade when, according to Arpaio, Trump sent him notes praising his questioning of Barack Obama's citizenship. ( Even after Trump walked away from birtherism, Arpaio, um, didn't.

In July 2015, Arpaio invited Trump -- then a newly announced and lightly regarded presidential candidate -- to come to Arizona to address the immigration problems facing the country.

"I love the Mexican people," Trump said at that rally . "I love their spirit. I respect Mexico as a country. Their leaders are much sharper and smarter than ours. ... They're killing us at the border and killing us in trade."

Less than a week before the 2016 Iowa caucuses, Arpaio formally endorsed Trump. "I have fought on the front lines to prevent illegal immigration," Arpaio said in a statement announcing the endorsement. "I know Donald Trump will stand with me and countless Americans to secure our border."

Then, earlier this summer, he went on trial in federal court in Phoenix for criminal contempt for allegedly disobeying a court order to end patrols targeting immigrants. (For much more on the case, read this .) In late July, he was convicted and is scheduled to be sentenced -- he could face six months in jail -- in October.

Arpaio, for his part, is totally in the dark about a potential pardon, but told Politico earlier this week that he would be ready if Trump wanted him to appear at tonight's rally. More recently, he's said he hasn't yet been invited.

"I've been doing rallies with him many, many times, and sometimes things are done the last minute," Arpaio said.