President-elect Joseph R. Biden Jr. plans to name Jaime Harrison as his pick to lead the Democratic National Committee, part of an effort to bolster the committee ahead of what are already expected to be challenging midterm elections for the party, according to two people with knowledge of the selection.
A former chairman of the South Carolina Democratic Party, Mr. Harrison became a national political star last year as he shattered fund-raising records in his race against Senator Lindsey Graham, who was up for re-election. While Mr. Harrison lost in November, drawing 44 percent of the vote to Mr. Graham’s 55 percent, he developed a broad bench of support across the party.
The selection of Mr. Harrison, on the heels of Mr. Biden’s victories in Arizona and Georgia in November, reflects the president-elect’s longstanding determination for Democrats to compete in once-red states, a recognition that the party will never sustain an enduring congressional majority without making inroads across the Sun Belt.
Mr. Biden’s top advisers are also planning to appoint a small group of elected Democrats as vice chairs to reward their support in the campaign and offer them the opportunity to be high-profile surrogates. Gov. Gretchen Whitmer of Michigan, Senator Tammy Duckworth of Illinois, Representative Filemon Vela of Texas and Mayor Keisha Lance Bottoms of Atlanta will serve in the roles.
Following the tradition of committee members deferring to the president’s pick, Mr. Harrison is not expected to face a challenger for the position.
Mr. Harrison is well known to the staff and members of the D.N.C., a result of his work heading the South Carolina state party and a failed bid to become chairman of the committee in 2017. (Tom Perez, the departing D.N.C. chair, won that race.) Mr. Harrison was championed by Representative James E. Clyburn of South Carolina, an influential Biden ally who helped the president-elect win the primary race in Mr. Clyburn’s home state. Mr. Perez opted against running for a second term.
Incoming presidents traditionally take control of the party committees, installing their own chair and staff members. Former President Barack Obama chose to try to establish his own political operation outside the committee, a decision that many D.N.C. members say damaged state parties and led to years of dysfunction at the national level.
Far more of a party institutionalist, Mr. Biden has promised to rebuild state parties and deepen investments in the committee.
Mr. Harrison was favored by state party leaders, who saw him as an ally in their effort to keep the committee focused on rebuilding local party infrastructure. After Mr. Biden’s election, dozens of state party chairs and vice chairs sent a letter to his transition team that did not name Mr. Harrison but listed a number of qualities that matched his experience and skills.
“We’re convinced that he not only believes in the organizing principle of state parties but that he will be a very loud voice with the Biden administration,” said Jane Kleeb, the chair of the Nebraska Democratic Party.
The focus on the national party committee comes as Democrats try to navigate a deeply uncertain electoral landscape. Even before the attack on the U.S. Capitol scrambled American politics, Democrats anticipated difficult House and Senate midterm races in 2022 and the lingering possibility that Mr. Biden — who will become the oldest president in the country’s history on Wednesday — may decide not to run for a second term.
But even before the midterms, the party committee will have to bridge the divides between Democrats who want Mr. Biden and his messaging to focus on unifying the country and a liberal wing eager to pursue prosecutions and other measures to hold President Trump and his allies accountable.
The role of Mr. Harrison’s home state in the early primary process could complicate discussions around changing the nominating process. South Carolina is the fourth state to hold a primary contest, a role that brings an influx of candidates, spending, news coverage — and an outsize say in the nomination fight.
The party faces broad concerns about the fairness of complicated caucus processes, as used in Iowa and Nevada, along with questions about how two relatively older, whiter states — Iowa and New Hampshire — cast the first two sets of votes. Already, some Nevada party leaders are pushing to end to all caucuses and to dethrone Iowa for the first round of voting.