BISMARCK, N.D. (AP) — U.S. Senator Heidi Heitkamp is apologizing for misidentifying victims of domestic violence, sexual abuse and rape who were listed in a recent newspaper ad aimed at her opponent.

Heitkamp said in a statement Tuesday that she had recently learned that several of the women named in the ad either hadn’t authorized it or are not survivors of abuse. She says she deeply regrets the mistake.

The ad that ran Sunday in several North Dakota newspapers was an open letter to Kevin Cramer, her Republican opponent, criticizing comments he made on Brett Kavanaugh’s confirmation to the Supreme Court .

Cramer supported Kavanaugh, while Heitkamp voted against his nomination.

The Heitkamp-Cramer matchup is seen as critical for control of the closely divided Senate.