Paras Griffin via Getty Images The ACLU's ad seeks to remind voters of Stacey Abrams' work with popular GOP Gov. Nathan Deal.

The American Civil Liberties Union is jumping into one of the defining contests of the 2018 midterm elections, spending $800,000 on a television ad aiming to boost Democrat Stacey Abrams in her neck-and-neck Georgia governor’s race against Republican Secretary of State Brian Kemp.

As a nonprofit, the group doesn’t officially endorse candidates. But the ad clearly aims to highlight Abrams’ work with popular outgoing GOP Gov. Nathan Deal on criminal justice reform issues.

The ad is the latest step in the 98-year-old civil rights’ organization’s quest to become more directly involved in electoral politics. It has worked this year to oust prosecutors who stood in the way of reform efforts and to stop infamous former Maricopa County Sheriff Joe Arpaio in Arizona’s GOP Senate primary. And it broke with years of tradition to oppose Brett Kavanaugh’s ultimately successful nomination to the Supreme Court.

“There is too much at stake for civil liberties and civil rights in Georgia’s gubernatorial race for us to sit on the sidelines this election,” said Faiz Shakir, the group’s national political director. “Georgia’s next governor should continue the bipartisan fight for criminal justice reform, specifically taking steps to reduce mass incarceration and the state’s dependence on private prisons, as well as prioritizing treatment over incarceration.”

The ad features a mother from the suburbs of Atlanta discussing how her son, a drug addict, was sentenced to six years in prison.

“Georgia spends millions keeping low-level offenders locked up,” a female narrator says in the ad. “Stacey Abrams joined Nathan Deal on bipartisan reforms to reduce costs, and Stacey Abrams will end dependence on private prisons, saving millions that could be used for treatment.”

Abrams and Kemp are in a tight race that pits a progressive state legislative leader who would be the first black female governor of any state in the country against an arch-conservative who has gained a reputation for suppressing voters.

On criminal justice issues, Abrams has proposed ending cash bail and private prisons in the state, restricting the use of asset forfeiture, increasing funding for diversion programs and decriminalizing marijuana. Kemp has opposed those reforms and has said he views private prisons as a form of “competition” for state-run facilities.

The ad also has the benefit of linking Abrams, who has been trying to woo moderate voters since the primary, to Deal, whose approval rating is typically above 50 percent. Deal has endorsed Kemp.

The ad buy is the ACLU’s largest of the cycle. The organization announced last week it was suing Kemp’s office over the state’s controversial “exact match” policy for voter registration.