WILMINGTON, Del. — President-elect Joseph R. Biden Jr. named Ron Klain, a veteran Democratic operative and a decades-long confidant, to be his White House chief of staff on Wednesday, the first step toward putting in place his administration’s senior leadership.
Mr. Klain, a lawyer with deep experience on Capitol Hill, advising President Barack Obama and in corporate board rooms, served as Mr. Biden’s chief of staff when he was vice president and has been seen for months as the most likely choice to manage his team in the White House. Known for steady nerves, he also has a fierce wit, which he has frequently unleashed on President Trump on Twitter.
He was particularly critical of Mr. Trump’s handling of the coronavirus pandemic, having served as the “Ebola czar” under Mr. Obama during an outbreak of the deadly disease in 2014. A video of Mr. Klain lecturing Mr. Trump about the pandemic was widely viewed during the campaign.
In a statement, Mr. Biden called Mr. Klain an “invaluable” adviser, noting in particular the work they did together during the economic crisis in 2009 and the Ebola outbreak.
“His deep, varied experience and capacity to work with people all across the political spectrum is precisely what I need in a White House chief of staff as we confront this moment of crisis and bring our country together again,” Mr. Biden said.
Mr. Klain has gone in and out of government over the past several decades, at times practicing as a lawyer and later working with Steve Case, the founder of AOL, in a venture capital investment firm called Revolution.
Mr. Klain thanked his well-wishers in a tweet on Wednesday night, saying that he was “honored by the President-elect’s confidence” and that he would “give my all to lead a talented and diverse team in a Biden-Harris” White House.
The choice of Mr. Klain, 59, who first went to work for Mr. Biden in the late 1980s when Mr. Biden was a senator from Delaware and Mr. Klain was a recent graduate of Harvard Law School, signals that the president-elect intends to rely on a tight circle of Washington insiders who have been by his side for years.
Advisers have said that Mr. Biden will announce other top White House staff members in the coming days, even as Mr. Trump refuses to accept the results of the election, tweeting “WE WILL WIN!” on Wednesday evening.
Mr. Biden is not likely to reveal his cabinet picks until around Thanksgiving, several people close to the transition said.