South Carolina U.S. Senator Jim DeMint will replace Ed Feulner as president of the Heritage Foundation. Mr. DeMint will leave his post as South Carolina's junior senator in early January to take control of the Washington think tank, which has an annual budget of about $80 million.

Sen. DeMint's departure means that South Carolina Governor Nikki Haley, a Republican, will name a successor, who will have to run in a special election in 2014. In that year, both Mr. DeMint's replacement and Sen. Lindsey Graham will be running for...