Those tensions came to the fore on January 29, when the FBI raided Melgen’s South Florida ophthalmology practice as part of a Medicare fraud investigation. The following day, the Herald reported that the FBI was also probing Melgen’s ties to Menendez—including allegations from a “shadowy tipster” that “the two allegedly hired underage prostitutes.” The prostitution claims soon began cropping up in other mainstream outlets. As Washington Post media critic Erik Wemple wrote at the time, it was apparently the FBI probe that “moved the prostitution matter from what Fox News eminence Bill O’Reilly termed ‘lascivious crap’ to what journalists term ‘fair game.’” Wemple also pointed out that an investigation “based on thin and shifty charges” is a flimsy peg to hang a story on.

On the whole, though, the media struck a reasonable balance, at least initially. Many reported in depth on the favors Menendez had allegedly done Melgen, including trying to persuade top federal health officials, who found that Melgen had grossly overbilled Medicare, that the findings were unjust. While some mentioned the prostitution claims, they did so in passing, and they stressed that the claims were dubious. In early February, for example, the Post noted that “the allegations—made by an anonymous whistleblower and first publicized on a conservative Web site—have not been verified independently.”

Those reporters who dug into the evidence found more reason for skepticism. The Miami Herald, which ushered the allegations into the mainstream, dispatched a team of reporters to the Dominican Republican to try to find the alleged prostitutes, based on names and contact information in the tipster’s emails. They turned up “shreds of evidence” that were consistent with Williams’s tale, but “no concrete links” tying Menendez to prostitution. As for the women in question, they were “nowhere to be found.”

The relative restraint with which the mainstream press handled prostitution allegations vexed conservative media watchdogs like the Media Research Center.

Then, in mid-February, something shifted. First, on Friday, February 15, the Post splashed a juicy headline across its site: “FBI Probing Allegations Sen. Menendez Patronized Prostitutes In Dominican Republic.” The following day, a variation of the story ran on page one of the paper. The probe had been public for weeks by this point. The Post added no new information on the prostitution front, except that the FBI had sent agents to the Dominican Republic to interview witnesses, and that it had “found no evidence to support the claim.” Some might argue that the FBI failing to substantiate unsubstantiated allegations, especially of the sort that can destroy a person’s reputation, is hardly grounds for rehashing them on A1. But other outlets followed suit, including Politico and The Hill, which ran pieces based on the Post’s reporting; the following Monday, CBS aired its segment, which “confirmed” an investigation was underway.

Most of these reports explained that the FBI had found little or no evidence to support the prostitution allegations. But the bold-face headlines hyping an official probe gave these claims new credibility; meanwhile, the better-founded allegations about Menendez using his influence to benefit a major donor became B-matter.

The shift in tone since has been palpable. While there have been few new developments in the case, over the last two weeks the mainstream press has run dozens of stories, columns, and blog posts about Menendez’s plummeting approval ratings, his response to the scandal, and the potential fallout. Most toss in the prostitution allegations with little or no context. “Unsubstantiated” has morphed into “allegedly”—as in, “Menendez is in hot water for flying to the Dominican Republic with Melgen, allegedly to visit prostitutes,” full stop. Rather than tell the backstory, many journalists mention offhandedly that Menendez “has denied” the allegations—or, worse, link to The Daily Caller report.

Mariah Blake writes for the United States Project, CJR's politics and policy desk. She is based in Washington, DC, and her work has appeared in The Atlantic, The New Republic, Foreign Policy, Salon, The Washington Monthly, and CJR, among other publications.