[12][13] On July 20, 2020, after the death of John Lewis, Williams was selected to replace him on the November ballot for Georgia's 5th congressional district in the 2020 election.

[14] The 5th is so heavily Democratic that Williams had been all but assured of a seat in Congress when she was selected to replace Lewis on the ballot.

[15][16][17] Georgia Governor Brian Kemp called a September 2020 special election to fill the remainder of Lewis's 17th term.

Williams opted to not run in the special election, choosing instead to focus on her role as party chair.

[18] The special election was won by Atlanta city councilman Kwanza Hall, who served for a month before handing the seat to Williams.

Williams held her seat in the 2022 elections against Republican Christian Zimm, by a smaller but no less overwhelming 65-point margin.

[20] Williams was one of two Democrats in December 2023 along with Bobby Scott to vote against the expulsion of now-former New York representative George Santos.