But neither of the candidates in the runoff has declared support for the commission, widely known as Cicig.

In the runoff, Sandra Torres, the former first lady, will compete against Alejandro Giammattei, the former prisons director. Ms. Torres won nearly 26 percent of the vote and Mr. Giammattei got 14 percent. Both have been in the sights of Cicig.

Ms. Torres, 63, who was making her second run for the presidency, was accused of campaign finance violations connected to her losing presidential campaign in 2015. The charges were not filed until after she began her campaign, giving her immunity as a candidate.

Mr. Giammattei, 63, was in charge of Guatemala’s prisons while an execution squad composed of high-ranking officials ordered the killing of prisoners. Although other government officials were convicted, a judge ordered the case against Mr. Giammattei dropped for lack of evidence. This is his fourth run for the presidency.