Few jobs are as demanding as the U.S. attorney general’s. The AG’s popularity peaks at the swearing-in ceremony and goes downhill from there. It’s not just the hard cases on the docket. It’s that attorneys general have two mandates that sometimes conflict. Do they follow their responsibilities as the nation’s chief law enforcement officer, wherever those responsibilities lead? Or do they act as the president’s top appointee in law enforcement and do his bidding?

AGs do not keep their jobs unless they know which mandate takes priority. They serve at the president’s pleasure.

This bedrock choice between blind justice and political calculation is almost certain to confront Loretta Lynch once the FBI concludes its investigation into Hillary Clinton, her top aides, and the Clinton Foundation.

Her choice just got tougher now that the former secretary of state is sure to win the Democratic nomination. She effectively clinched that prize with an unheard-of 50-point victory over Bernie Sanders in Saturday’s South Carolina primary, on the heels of a solid victory in Nevada last Tuesday. Clinton's victory in the Palmetto State portends big wins all across the South, leaving Sanders with no realistic path to the nomination. After months of enthusiastic “Feel the Bern” rallies, the Democrats are now back where they started. As one prankster, who managed to photo-bomb a Clinton campaign rally, put it on his tee-shirt: “Settle for Hillary.”

Before Democrats officially settle, though, Clinton, Lynch, and Barack Obama have a treacherous bridge to cross.

Standing athwart it is FBI Director James Comey, an experienced prosecutor and consummate professional with some 100-150 agents investigating the Democratic front-runner, the Clinton Foundation, and (presumably) several of Hillary’s closest aides: Huma Abedin, Cheryl Mills, and Jake Sullivan.

Clinton voters are oblivious to the dangers. Polls show they no longer consider her “honest and trustworthy,” but they still don’t think she has committed any crimes. Countless Clinton supporters have told me, “These investigations won’t find anything. The Benghazi hearings proved it. This is simply a partisan witch hunt.”

They are half right. The Benghazi hearings proved, once again, that Congress has the investigative prowess of Homer Simpson. They are right that Republicans hate her. Divided as the GOP is, it is united in thinking Bill and Hillary are corrupt, self-serving liars.

But the GOP is not leading the criminal investigation. The FBI is. The bureau is not partisan, and it is not on a witch hunt. Despite the obvious risks of investigating the presumptive Democratic nominee during a Democratic administration, its agents are sorting through mountains of evidence pointing to serious, deliberate crimes.

What are the key legal dangers facing Clinton and her aides? Here are just a few.

* Hillary Clinton deliberately set up a private email server for herself and her top State Department aides. She used it to store over 1,800 documents now deemed classified, some highly classified. The sheer bulk of the security violations is extraordinary. Intelligence professionals agree the server was almost certainly hacked by foreign agencies—probably by several.

* Secretary Clinton specifically instructed aides to send her classified materials on that insecure network. We know of at least one such instruction. We don’t know how many others were redacted by the State Department.

* Because her server was private, the State Department’s records did not include its contents when responding to Freedom of Information Act requests. The department wrongly told FOIA applicants that no such materials existed. Not only did the materials exist (on Clinton’s server), senior officials knew it and allowed false denials to be made.

* Some documents on the Clinton server contained the intelligence-gathering methods, the names of undercover agents, and real-time disclosures of top officials’ movements. Aside from the nuclear launch codes, these are the most closely guarded secrets in the U.S. government. That material is “classified at birth,” as Clinton, Mills, Abedin, and Sullivan certainly knew. To avoid any misunderstanding, they had all taken mandatory training in the proper treatment of sensitive and classified materials.

* Some of the classified materials on Clinton’s server originated in intelligence agencies outside the State Department and came into the department on a secure, classified network. They were marked as such. They could only be transferred to Clinton’s unsecured network by hand. Each occurrence was a felony. Since the server has now been recovered, the FBI and intelligence agencies know who sent those messages and who received them at the State Department.

* The Clinton Foundation and some private businesses were deeply involved in the State Department’s business. The lines were blurred between Hillary Clinton’s official role as secretary of state and her unofficial role at a major foundation, headed by her husband, that was showered with money from people and companies working with the State Department. At best, the arrangements were sleazy. At worst, they were criminal “pay to play.”

* Hillary’s closest aide, Huma Abedin, had blurred roles, too. While working at State, she was also employed by a private company whose clients did business with her department and the government.

One major feature of FBI investigations has been completely ignored. The bureau normally interviews all the key participants, and it knows the answers before it asks the questions. That should mean closed-door sessions with Abedin, Mills, Sullivan, and, ultimately, Hillary Clinton and perhaps Bill Clinton (if the foundation’s activities are at issue). Failing to interview them would replicate the botched Benghazi investigation by Adm. Mike Mullin and Ambassador Thomas Pickering. The FBI won’t repeat that mistake or subject itself to the withering criticism.

These interviews are deadly serious. Former Speaker of the House Dennis Hastert learned that the hard way. When the FBI asked why he had withdrawn cash from his bank account, he lied. He was caught and, last October, plead guilty to a felony.

So, will Abedin, Mills, or Sullivan answer fully and truthfully or invoke their Fifth Amendment rights? If they did, would it become known and hurt Hillary politically? If she refuses to testify herself, her political career is over. She won’t do that unless she fears indictment is certain, and she would have to drop out of the presidential race anyway.

If FBI Director Comey does recommend criminal charges, he will put DOJ and the White House in a very tight box. First, as a seasoned prosecutor, he will present only strong, winnable cases. Second, he won’t present one or two charges. He will present evidence of dozens and dozens of felonies. AG Lynch and her career attorneys won’t be able to say, “On the whole, there’s just not enough here to convict.” They will have to say that over and over, on each charge. Indictment on even a few felonies is a torpedo beneath the waterline for Clinton. Third, it is clear that CIA and FBI investigators already fear an administration whitewash and have leaked damaging information to the press.

If insiders think the administration is engaged in a full-fledged cover-up, they will resign, led by Comey. They won’t go quietly. They will spill the beans. And two hours later, it won’t smell good.

Knowing that, Lynch and her political bosses, Barack Obama and his closest adviser, Valerie Jarrett, will have to decide which is worse, indicting their party’s presumptive nominee or risking their own Watergate?

Whichever they choose, the White House will not want its fingerprints on the decision. They will want White House spokesman Josh Ernest to say, with a straight face, “This decision was made entirely by respected, career professionals at the Department of Justice.”

If the FBI recommends felony charges, as is likely, the DOJ’s choices are damned-if-you-do, damned-if-you-don’t. For Loretta Lynch, it will make for a painful final year. For her party, the stakes are the presidency. For her country, they are the impartial rule of law.