Sen. Joni Ernst, a Republican of Iowa, decided not to seek re-election for a third term, two people familiar with the decision and are ready to make the announcement next week.
Ernst has been working on this decision for months, but has started telling friends in recent days. Her retirement established an open Senate seat in Iowa.
A Republican official said Rep. Ashley Hinson was planning to compete. The crowded field of Democrats is already running.
CBS first reported Ernst's decision.