President-elect Joe Biden has selected his longtime aide Ronald Klain to serve as White House chief of staff in his incoming administration, the Biden-Harris transition team announced on Wednesday.

Klain, 59, will serve as a senior adviser to Biden and help to build out the administration’s leadership team. The Democratic operative previously worked as a senior adviser to the Biden-Harris campaign and served as the former vice president’s chief of staff within the Obama administration from 2009 to 2011.

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“Ron has been invaluable to me over the many years that we have worked together, including as we rescued the American economy from one of the worst downturns in our history in 2009 and later overcame a daunting public health emergency in 2014,” Biden said in a statement. “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.”

Ron Klain, former White House Ebola response coordinator, speaks during a House Homeland Security Subcommittee hearing in Washington, D.C., U.S., on Tuesday, March 10, 2020. President Donald Trump today spoke to the Republicans at their weekly conference lunch at the Capitol as his administration prepares a package of economic measures to combat the fallout from the coronavirus outbreak. Photographer: Andrew Harrer/Bloomberg via Getty Images

Klain was considered a frontrunner for the role due to his long working relationship with the president-elect. He advised Biden during his previous presidential runs in 1988 and 2008.

As White House chief of staff, Klain will play an instrumental role in crafting and executing the Biden administration's policy goals, including its efforts to combat the coronavirus pandemic. Former President Barack Obama tasked Klain to lead government response to the Ebola outbreak from 2014 to 2015.

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“It's the honor of a lifetime to serve President-elect Biden in this role, and I am humbled by his confidence," Klain said in a statement. "I look forward to helping him and the Vice President-elect assemble a talented and diverse team to work in the White House, as we tackle their ambitious agenda for change, and seek to heal the divides in our country."

Klain has worked within Democratic administrations for decades, serving as chief of staff to former Vice President Al Gore in the Clinton White House. He worked as an associate counsel to former President Bill Clinton and aided in the appointment of federal judges.

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As chief of staff to Gore, Klain played a key role in the former presidential candidate's effort to force a recount in Florida during the 2000 presidential election. The weeks-long battle culminated in a Supreme Court ruling that stopped the recount and effectively confirmed George W. Bush as president.

The Biden-Harris transition team is expected to announce more cabinet picks over the next several days.

President Trump has yet to concede defeat in the 2020 election and launched legal challenges over voting results in several states. Meanwhile, the Biden-Harris team has begun preparations for the transition and accused the Trump administration of withholding critical resources as his campaign pursues claims of election fraud.