A former Democratic congressional aide pleaded guilty Tuesday to sexually assaulting two women in 2010.

Donny Ray Williams Jr., 37, who served as a staff director for the Senate Homeland Security and Governmental Affairs subcommittee, pleaded guilty to third-degree sexual abuse, two misdemeanor counts of sexual abuse and one count of misdemeanor threats.

Prosecutors say that on July 22, 2010, Williams invited a female congressional colleague to his Capitol Hill apartment and promised to introduce her to Senate employees. At the house, prosecutors said, Williams spiked a drink with Ambien. The woman, according to court documents, fell into a “deep sleep,” at which point Williams raped her.

A month later, prosecutors said, Williams invited another woman to his home and gave her alcoholic beverages. They said he had sexual contact with her when she was too intoxicated to give her consent.

Williams had been indicted on 10 counts, but prosecutors agreed to dismiss the remaining charges. As part of the plea agreement, prosecutors said they would seek a suspended prison term and five years of supervised probation. Williams also would have to register as a sex offender for 10 years.

Donny Ray Williams, Jr. leaves D.C. Superior Court after a hearing on Aug. 31, 2012. (Susan Biddle/For the Washington Post)

The plea deal must be approved by D.C. Superior Court Judge Robert E. Morin who is scheduled to sentence Williams on March 6.

In an 2012 interview, Williams said the allegations were “absolutely and completely false.”

Williams began his Capitol Hill career in 1999. He worked for panels chaired by Sens. Joseph I. Lieberman (Conn.) and Mary Landrieu (D-La.). He also said he worked for Sen. Herb Kohl (D-Wis.), Rep. Elijah E. Cummings (D-Md.) and Rep. Jan Schakowsky (D-Ill.).