The son of Arizona Sen. Jeff Flake wants a new civil trial against former Phoenix-area Sheriff Joe Arpaio, a candidate for the seat Flake is vacating.

Austin Flake and his ex-wife, Logan Brown, lost a malicious-prosecution case against Arpaio in December. They accused the sheriff’s office of bringing an unfairly heavy-handed case against them after 21 dogs died of heat exhaustion in 2014 at the kennel Brown’s parents owned, and which Flake and Brown were maintaining while the owners were away.

They are seeking another trial because authorities did not turn over key evidence that would have convinced the jury in Flake and Brown’s favor, their attorney Stephen Montoya told, The Associated Press.

The evidence involves a graph created by authorities that accurately showed electrical usage dropping inside the kennel, the AP reported.

Arpaio’s office at the time recommended animal cruelty charges against Flake and Brown. But prosecutors requested the case against the Flakes be dismissed, and the owners of the kennel eventually pleaded guilty, saying the air conditioner failed because operators didn’t properly maintain it.

Austin Flake’s suit claims that Arpaio’s case was meant to do political damage to his father, an Arizona GOP senator, and to burnish his own image.

Arpaio has cultivated a national reputation as “America’s Toughest Sheriff” for his controversial stringency on illegal immigration, investigating former President Barack Obama’s birth certificate, and employing racial-profiling methods.

President Donald Trump pardoned Arpaio in August after the sheriff was convicted in July of contempt of court. Flake criticized Trump’s decision at the time.

Arpaio announced his hard-line conservative candidacy for Jeff Flake’s seat in January, joining Republican Rep. Martha McSally and former state Sen. Kelli Ward on the party’s primary ballot. Flake is retiring at the end of his term in 2019.

Austin Flake claims the distress of Arpaio’s criminal investigation against him led to the demise of his marriage to Brown.

Flake said in court testimony in December that he suffers from anxiety and cycled through six types of antidepressants.

He also said Brown suffered panic attacks during the investigation, and the stress led to constant fighting between them.

“Things just got to a point where we were bringing out the worst in each other. … We couldn’t get on any grounds to make it work,” he said.

Jeffrey Leonard, an attorney representing Arpaio and Maricopa County, declined to comment on the prospect of a new trial, the AP reported.

— Eric Garcia contributed to this report.Watch: No Elves, No Coal: Myth-Busting the Capitol’s ‘Little Doors’