The still-uncertain election results are presenting new obstacles, however, for the dozens of Democratic officials who have been working for months to set up a government in the event of a Biden win. The emerging likelihood of a Republican-controlled Senate, for one, has forced Biden aides and outside advocacy groups to reevaluate both the policies they would aim to pass through Congress and the people they would nominate for Cabinet posts and judicial vacancies.

"The American people will determine who will serve as the next President of the United States," a Biden-Harris Transition spokesperson said in a statement to POLITICO. "The crises facing the country are severe — from a pandemic to an economic recession, climate change to racial injustice — and the transition team will continue preparing at full speed so that the Biden-Harris Administration can hit the ground running on Day One.”

Presidential transitions typically move at a breakneck speed even in smoother election cycles, given that teams have just over two months to stand up a federal bureaucracy staffed with more than 4,000 political appointees. Any delay in the election result this year will narrow that window, giving the Biden team an even shorter runway to begin formally vetting Cabinet nominees, laying out policy priorities and crafting an agenda.

Some of their work can continue unfettered, even as ballots are counted and legal fights play out. The transition team has the ability, for instance, to conduct FBI background checks on potential Cabinet nominees. But officials do not have the ability to work with the Office of Government Ethics — a secondary step in the vetting process — until the election results are final. Past transitions have typically begun providing the OGE with names to review by early or mid-December.

In other areas, they may have their hands tied. Teams of officials are not allowed to enter federal agencies until after the election is over, restricting their ability to start learning the lay of the land in each department. A drawn-out race would mean a delay in working with current federal employees to identify critical decisions and quick actions that can be taken in each agency, as well as in collecting information to brief future political appointees on their department.

Any attempts by Trump and his allies to contest the results and throw up roadblocks could also hurt the Biden team’s ability to prepare to take over, the source close to the Biden transition said.

“It's somewhat dependent on whether or not Trump can transition through the stages of grief a little bit more constructively and quickly than he so far has,” the source said, flagging in particular the question of whether the current administration would withhold data on the severity of the coronavirus pandemic or progress on a Covid-19 vaccine.

Meanwhile, the Covid-19 pandemic is still raging. And while Biden has pledged a shift away from the Trump administration’s “leave it up to states” approach to the virus — and even began putting together his own shadow task force in the lead up to the election — a drawn-out contest could hinder his team’s ability to prepare their pandemic response.

Several states hit new record high case counts on Wednesday, and more than 50,000 people are currently hospitalized across the country. Public health experts warn the spread of the virus is likely to get much worse in the coming months, between holiday travel and colder weather prompting people to gather indoors.

Biden has laid out plans to create and fund a national plan for testing and contact tracing, release stronger public health guidance and push holdout governors to implement mask mandates. Much of that work would take place at the agency level, but coordination with career staff can’t begin with the results of the election up in the air, worrying health groups as cases continue to rise.

“We need to implement a scientifically based infection response as soon as possible to prevent more deaths,” said Frederick Isasi, the executive director of the health care advocacy group Families USA, on a call with reporters Wednesday. “It's the most central issue. So any delay in Biden’s ability to begin that work is our number one concern.”

The still-emerging election results, which suggest a far narrower win for Biden than polls predicted, may also force his team to reevaluate how much popular support they’re likely to have both for their pandemic response plan and a number of policy priorities — from climate legislation to immigration reform.

A delayed start to the transition is not unprecedented: George W. Bush’s team in 2000 could not formally begin until mid-December, leaving them with roughly half as much time as other presidents-elect. But transition officials at the time followed Dick Cheney’s directive to “assume we’re going to win this thing” and continue their work unabated, Clay Johnson, who led the transition for Bush, said on a recent podcast.

Biden’s team has adopted a similar attitude this year, and they are publicly exuding confidence that the former vice president’s lead in critical Midwestern states will hold. Though they may be delayed in entering the federal agencies, people close to the transition say the significant government experience that Biden and many of his officials have means an ongoing delay won't be nearly as problematic.

Bush officials, for their part, went on to have more political appointees confirmed by the Senate in their first year in office than any other president. Andy Card, Bush’s chief of staff, later called the delay caused by the Florida recount “a blessing.”

“The president-elect and I had a wonderful time working under the radar screen,” Card said at an event hosted by the Partnership for Public Service in October. “Because most people were focused on what was happening in Florida.”