Hardman, the CEO of nonprofit Lutheran Services of Iowa and a member of the West Des Moines City Council, becomes the first Black woman elected to the 50-member Senate.
Hardman, a member of the West Des Moines City Council, won the left-leaning suburban seat, which was left vacant in October after its incumbent, who was also a Democrat, died from an illness.
Voters in a Democratic-leaning West Des Moines-area district will pick a new state senator Tuesday in a special election that could allow Iowa Republicans to regain a supermajority in the chamber.