GREENVILLE, S.C. — Newt Gingrich‘s presidential campaign Wednesday night sought to limit any damage from an ABC News interview with the thrice-married candidate’s second wife, releasing an open letter from his daughters to officials at the network.

ABC plans to air an interview with Marianne Gingrich Thursday night on Nightline, after the second and final debate before the South Carolina primary on Saturday. Ms. Gingrich was married to the former House speaker for 18 years. After they divorced, Mr. Gingrich married his current wife, Callista, with whom he had an extramarital affair.

The TV interview was disclosed Wednesday evening by the Drudge Report, touching off a firestorm in media and political circles, and prompted the Gingrich campaign to send out the letter to ABC, signed by Kathy Lubbers and Jackie Cushman, Mr. Gingrich’s daughters from his first marriage.

“ABC News or other campaigns may want to talk about the past, just days before an important primary election,” the two wrote.”But Newt is going to talk to the people of South Carolina about the future” and issues such as job creation.

They continued, “We will not say anything negative about our father’s ex-wife. He has said before, privately and publicly, that he regrets any pain he may have caused in the past to people he loves.”…