Paul Sancya, Associated Press
Republican presidential candidate, former House Speaker Newt Gingrich, speaks at the Personhood USA forum in Greenville, S.C., Wednesday, Jan. 18, 2012.

NEW YORK — ABC News plans to air an interview with the second wife of Republican presidential contender Newt Gingrich on its program "Nightline" just two days before the GOP's South Carolina primary.

An ABC News spokesman, Jeffrey Schneider, said Wednesday night that excerpts from the interview with Marianne Gingrich will be released during the day Thursday.

Those excerpts are expected ahead of both a Republican candidate debate Thursday evening in Charleston, S.C., and "Nightline," ABC's late-night news program.

ABC News hasn't indicated what Marianne Gingrich says in the interview. Her ex-husband has said that they don't have a relationship.

The interview comes as Gingrich is trying to topple GOP front-runner Mitt Romney by casting himself as the more conservative option in the GOP presidential race.