South Carolina Gov. Nikki Haley is expected to name Rep. Tim Scott (R) to replace outgoing Sen. Jim DeMint (R).
The New York Times reports that "Republican officials" say Scott, DeMint's preferred pick to fill his seat, is Haley's final choice.
She will make the formal announcement at noon.
Scott would hold the seat until a special election in 2014 when South Carolina voters will decide who will finish the last two years of DeMint's term. He will be the first black senator from the South since the 1800s.
The governor had previously said that she would not choose a "caretaker" for the seat, indicating her choice will be expected to run in 2014.
Scott's appointment would open up his seat, in a solidly Republican district, for a special election early next year.