Hillary Clinton hasn’t won the election yet, but she probably will. And if she does, her transition will swiftly face a fundamental question with profound consequences for all the other choices she makes as she builds out her team: What happens to the Cabinet and sub-Cabinet that’s already in place?

Officially, of course, everyone who serves at the pleasure of the president is prepared to leave when he does. But the cast of presidential appointees in the United States is enormous — there are more than 3,000 jobs to be filled — and it’s natural to think that many of those jobs will be filled in a Clinton administration by some of the people who are already filling them in the Obama administration.

The details, however, are a bit fuzzy both because it’s entirely at the discretion of the president and because there’s not much in the way of legal precedent. Same-party transitions that don’t result from the death or resignation of the incumbent president are quite rare. There’s the Reagan-Bush transition of 1988 (which retained Reagan’s Treasury secretary, attorney general, and secretary of education), and then you have to go 60 years further in the past to the Coolidge-Hoover transition to find another one.

In the more common case of a VP stepping up mid-term, the practice followed by Presidents Ford, Johnson, and Truman was to preserve a great deal of continuity, leaving the existing Cabinet in place initially and then rolling in new people over time. This in part reflects the exigencies of a crisis situation as well as the fact that the vice president is, himself, a member of the incumbent administration. But it also offers some considerable practical advantages that may weigh on Clinton’s mind.

Continuity offers convenience

The enormous advantage of a continuity-based transition strategy is that it offers massive convenience. The Obama administration already has in place a diverse and well-qualified team of Democrats running the executive branch of the United States. They have been vetted by the FBI and the press, and — crucially — confirmed by the United States Senate.

A continuity-focused Clinton administration would still replace the bulk of the existing White House staff with people from the campaign and the broader Clinton universe, but would basically skip the need to select and confirm a whole new set of Cabinet officers. With Loretta Lynch already in place as attorney general, after all, you don’t give Senate Republicans a chance to grill a new nominee about old emails and you don’t give Senate liberals a chance to grill a new nominee about criminal prosecutions of Wall Street banks. If you let Jacob Lew continue to serve as Treasury secretary, then you don’t need to thread the needle of finding a candidate acceptable to the Warren/Sanders wing of the party who also won’t rattle financial markets.

That kind of convenience is a luxury few recent administrations have had. But it would be very useful in terms of allowing the transition team to focus on Clinton’s early policy agenda, get a jump start on working with Congress, and address sub-Cabinet issues that often take months to get straightened out.

Even today, many important jobs — ranging from the assistant attorney general for antitrust to the assistant secretary for financial stability in the Treasury Department — lack a confirmed nominee. Keeping the bulk of Obama’s personnel in place would let Clinton get the federal government fully staffed in record time while swiftly pivoting to her unique opportunity to remake the federal judiciary.

The advantages of a new team

Keeping continuity sounds good, but you have to consider the basic reality that President-elect Clinton would probably like to have her own team in place. Clinton has pledged to appoint a Cabinet that’s half women, for starters, which would require her to get rid of some of the men who are currently in place. There are also basic questions of loyalty — Commerce Secretary Penny Pritzker is in the Cabinet largely due to her personal relationship with Obama. UN Ambassador Samantha Power has Cabinet rank, but also rather famously publicly called Hillary Clinton a “monster” in 2008 and may not be the president-elect’s favorite diplomat.

A victorious presidential campaign normally generates a vast array of ex-staffers who are owed jobs in the new administration.

Some of them — especially the more senior ones — will end up on the White House staff in the Executive Office of the President. But it’s also normal for more junior campaign staffers to end up scattered around to the various agencies. That’s easier to do when the people in charge of those agencies directly owe their jobs to the new president.

A half-transition is tough

The most natural approach is probably the one that was, in fact, chosen the last time we had a same-party transition — do a little of both.

George H.W. Bush replaced most of Reagan’s Cabinet but did retain three secretaries in their jobs while shifting Elizabeth Dole from the Department of Transportation to the Department of Labor. This kind of approach would let Clinton accomplish key goals while also taking advantage of the upsides of having many confirmed nominees already in place. It also makes sense from a basic talent point of view — if you simply rule out everyone who is already working in the Obama administration for a job in the Clinton administration, you are ignoring a huge number of experienced and ideologically like-minded people.

The problem is this could get very messy. The essence of a normal partisan transition is that it’s not personal. You and your colleagues haven’t been fired; your party just lost an election. From Election Day to Inauguration Day, your responsibility is to wrap things up and hand the reins over to the new team — and despite all the bitterness in American politics, the past two transitions have done that very well.

A same-party transition that offers neither a clean break nor total continuity disrupts that. Many officials will be trying to keep their existing jobs rather than preparing to hand things off to a successor. Others will be angling for promotions.

And for those who are asked to leave, it will be personal. The new president decided, for whatever reason, that she didn’t want you in the job even though many similarly situated people were kept on. That’s a recipe for ill will and chaos. It’s also, realistically, probably somewhat unavoidable when you consider the practical disadvantages of firing the entire Obama administration en masse.

The best Clinton can hope for is to make a fast, clear, and decisive statement about whom she wants to stay — even though in a practical sense that may mean needing to make some early calls on some of the lower-profile agencies whose leadership typically doesn’t get sorted out until after Election Day.