PHOENIX (AP) — The Democrat in the Maricopa County sheriff's race filed a defamation lawsuit Thursday against incumbent Joe Arpaio over a TV ad that claims the challenger assaulted his ex-wife 13 years ago during an argument. Democrat Paul Penzone denied the allegations made in the commercial that the Republican sheriff started running this week, saying his opponent ran the ad knowing the allegation was false. City prosecutors in Glendale declined to prosecute either person because there were conflicting accounts without any independent witnesses and no reasonable likelihood of winning convictions. The challenger said in a campaign video earlier this week that Arpaio apologized to him late last year for running a 2012 ad, but he said the sheriff has since changed course.