I've been doing some reading and while this won't necessarily provide anything "new", I felt it important to share a lengthy, pre-2016 source of information pertaining directly to Arpaio's involvement in the alleged 400(or more?) cases of sexual assault against children, which were not investigated or which were otherwise 'botched' by the department(s)/employees under his command.

Read all 3 pages (source: http://archive.boston.com/news/nation/articles/2011/12/04/critics_tough_sheriff_botched_sex_crime_cases/))

page 1: http://archive.is/HSC0k (source link + "?page=1")

page 2: http://archive.is/rDfHd (source link + "?page=2")

page 3: http://archive.is/35fjf (source link + "?page=3")

Note: this part at the end really got my attention...

In their follow-up on the case of the 13-year-old attacked by the man claiming to have a broken car, El Mirage police discovered Arpaio's office hadn't interviewed the victim.

An El Mirage detective went to the girl's home just off the city's main drag. The girl's uncle said she and her mother weren't around and took the investigator's card with a promise to ask them to call.

The mother never called back. She and her daughter's whereabouts are unknown.

The case of the molested 3-year-old was returned to El Mirage police unworked five months after the initial report. The family's beige tract home was deserted, the phone disconnected.

This is surely a point of concern, set aside arguments about racism/immigration and such for a moment - the focus point is Arpaio's blatant disregard for minors who are victims of abuse & that alarm bells should most certainly be raised about Trump's pardoning of Arpaio - albeit that a pardon confirms guilt.

Sorry if the connection isn't already apparent, feel free to suggest improvements to the post, if any rules are broken or at risk of being broken.