WASHINGTON — Representative Tim Scott of South Carolina, who arrived in Congress two years ago on the wave of the Tea Party movement, was appointed on Monday to succeed Jim DeMint in the United States Senate, an elevation that makes him the first black senator from the South since the late 19th century.

When he is sworn into office on Jan. 3, Mr. Scott will be the sole African-American in the Senate and only the fifth to serve since the Reconstruction era after the Civil War. He must seek election to the seat in 2014, a contest that will be viewed through a historical lens in the state that became the first to secede from the union after Abraham Lincoln’s election in 1860.

Mr. Scott, 47, will become a rising Republican in a party that is searching for new leaders in the wake of the nation’s rapidly changing demographics. He has built a strong record of conservatism, both fiscally and socially, and pledged on Monday to adhere to those principles in the fiscal debate in Washington.

“Our nation finds itself in a situation where we need some backbone,” Mr. Scott said during a news conference in Columbia, S.C. “We need to make very difficult decisions.”