The following post is written by Bill Levin, my friend and former colleague from the Office of Legal Counsel. He has written in this space before.

With fewer than 50 days to the start of the Democratic convention, the legal and political peril of Hillary Clinton has reached its climatic phase. Her career has come full circle, from a staffer in the Watergate proceedings to the lead in Emailgate, with two presidencies in the balance.

Prior to the recent State Department IG Report, it was widely believed that Mrs. Clinton could weather the storm. The FBI has avoided official comment, except to call the process an investigation and not an invented “security review.” Only in the last week has the White House acknowledged the obvious, that it is a “criminal investigation.” Major leaks are now appearing daily—CIA operatives may have been named and the emails contained highly classified discussions of drone strikes in Pakistan.

With the absence of rebuttal as a license, Mrs. Clinton spins excuses. The serial misstatements have been disseminated by a willing press for more than a year. It was for convenience. It was permitted. It was legally allowed. They were not marked. And the latest, and weakest, post-IG Report: It was done before so I thought it was allowed.

The IG Report demolishes the lies, from an unimpeachable source. As an Obama appointee, the Inspector General, Steve Linick, cannot be credibly depicted as a Kenneth Starr setting upon Mrs. Clinton from the vast right. Not that it has deterred Team Hillary from making the attempt. But the report has issued from the State Department itself. Hence the new damage.

The flaw in the report is structural. It lays out violation of policy. In the Clintonian universe, as executed by the press, an accusation short of criminality is a political free pass. Which brings matters to handicapping the indictment.

My expectation is that Director Comey of the FBI will seek a referral for indictment. This seems sensible given its extensive investigation, the IG factual record, and the potential connection to Clinton Foundation misdeeds.Plus, at least two individuals, Bryan Pagliano and the Romanian hacker, Guccifer—and likely more, including Cheryl Mills, and possibly other close aides—have been granted at least limited immunity.

In addition, the disclosure that highest national security secrets were compromised is uncontested, and there are multiple attempts to hack the server. These seem to invite action under the gross negligence or willful standard of the relevant criminal statutes. So the betting line has narrowed to whether DOJ leadership or the White House will approve an indictment.

The received wisdom is decidedly, and wisely, that no indictment will issue. President Obama has downplayed the scandal given that Mrs. Clinton is the standard bearer of his “legacy.” She will joylessly trudge to the nomination, in all but the most extreme conditions. Unless and until Democratic leaders perceive her as weakened beyond repair, the playbook is set.

Yet Donald Trump should pray that no indictment issues. Events then play to his strength, handing him the defining issue to ride to the Presidency.

The spectacle would be resignations from the FBI, led by Director Comey, assuming reports of his integrity are accurate, and possibly other members of the outraged classified community. They will be duly, if implausibly, vilified as political hacks. The ironic echo of Nixon’s firing of Archibald Cox during Watergate will generally be left unreported by the press. But it is simply too big a story to ignore, especially if this unfolds in July, as serious attention shifts to the conventions.

For Mr. Trump, the news blunts and overwhelms the coming attacks. The worst that can and will be said of Mr. Trump personally, nastiness and temperament issues aside, is that he took advantage of laws and rules to make money in business.

Of Hillary the worst that will be said is that she risked government secrets and violated her one sacred duty to protect and defend the United States. The charge is reinforced by the large contributions received from interested nations by the Clinton Foundation. Mr. Trump can be counted on to use the buried indictment as a blunt and effective cudgel.

A non-indictment would implicate Mr. Obama and his Justice Department in the cover-up. It would set up Mr. Trump’s main line of attack: eight years of empty recovery, betrayal of the American worker, and lies by a President and administration deserving to be excoriated.

How could Mr. Trump seal this latter deal? With one promise: “As President, one of my first acts will be to seek the indictment of Hillary Clinton.” Out with President Obama and a corrupted Justice Department. The press would drop with the vapors.

Mr. Trump would send a powerful message of accountability. He could broaden it with a commitment to reform the Internal Revenue Service, the Veterans Administration, and the Environmental Protection Agency. Voters would be energized, and even conservatives would be excited if a platform were developed addressing the overreach of the administrative state. Not incidentally, the promise would put Hillary in the unenviable position of running for President to save her own skin and reputation.

It is possible, and perhaps even likely, that Hillary Clinton will escape indictment for her actions. And be rewarded with the Presidency.  James Comey is seemingly the last realistic line of defense. Will he resign prior to the Democratic convention or let the clock run out, until it is too late to matter?

It is legitimate to ask if the Orlando massacre changes the calculus. Mr. Comey, the seventh director of the FBI, is only three years into his ten-year term. As one of the best public servants available to head the agency in such perilous times, his resolution of the indictment dilemma is fraught with significance.

Mr. Levin, a graduate of Yale Law School, manages a financial advisory and investment firm in New York.