A spokeswoman for Paul Penzone, the Democratic challenger for Maricopa County Sheriff, tells ABC15 that Penzone plans to file a lawsuit against Maricopa County Sheriff Joe Arpaio on Thursday.

A press conference is scheduled for 2 p.m. Thursday.

Penzone said in a news conference earlier this year that he would take legal action if Arpaio ran attack ads claiming he abused his ex-wife, stemming from a 2003 altercation. Penzone narrowly lost to Arpaio in 2012.

A new Arpaio attack ad surfaced this week surfaced claiming Penzone "assaulted" his ex-wife.

In a YouTube video posted Monday, Penzone responded to the ad, noting that Arpaio is trying to use it to win an election.

Arpaio's campaign said in a statement that they are "not concerned" about Penzone's lawsuit threat.

"Every embarrassed politician threatens to file a lawsuit—but so far, Paul Penzone’s law firm hasn’t identified a single inaccuracy in the ad," part of the statement read.