A BLOWHARD blogger’s slur against first- lady-to-be Melania Trump — the baseless allegation that she once worked as a high-end escort at a gentleman’s club in Italy, before meeting her husband — is a loathsome canard. So is the similarly “fake news” falsehood that a Northwest Washington pizzeria is a front for a child sex-abuse ring run by Hillary Clinton, and so is the “birther” rubbish championed by Donald Trump, which sought to cast doubt on President Obama’s legitimacy as chief executive.

So it is easy to sympathize with Ms. Trump, who has brought a defamation lawsuit in a Maryland court against the blogger, Webster Griffin Tarpley, who lives in Montgomery County, as well as the Daily Mail, a British tabloid that also published the lie. No one — no first lady, no president, no business owner and no private citizen — should be expected to tolerate an outrageous and fabricated smear campaign. Those who are on the receiving end of “fake news” have every right to strike back.

Ms. Trump is hardly the first first lady to be tarred by hateful lies. Michelle Obama has had to contend with vile online attacks since her husband first ran for president, including a racist slur not long ago by a nonprofit official in West Virginia, Pamela Taylor, who referred to the first lady as an “ape in heels.” Rachel Jackson, Mary Todd Lincoln and others also were the targets of cruel attacks. What has changed, owing to technology, is the slander’s reach. Hundreds or thousands might be exposed to a whispering campaign or a pamphlet; a blog post might go viral and slime its subject in the eyes and ears of millions.

In Ms. Trump’s case, she demanded a retraction and apology from Mr. Tarpley, who published his sordid blog post on Aug. 2. He complied, whimpering that he’d just repeated a rumor that had appeared on the Internet — in other words, fake news, the fast food of ignoramuses everywhere. Despite the retraction and apology, Ms. Trump went ahead with the lawsuit, filed in Montgomery County Circuit Court this fall.

Ms. Trump’s lawyers are justified in asserting that the allegations about Ms. Trump are false, and that Mr. Tarpley and the Daily Mail “broadcast their lies to millions of people throughout the United States and the world — without any justification.” Whether the “fake news” peddler is a nobody in Gaithersburg or the president-elect, the product is noxious, and harm can be real.

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Whether a lawsuit by a future first lady against an unknown blogger is the optimal way to combat fake news is another question. As a public figure, Ms. Trump may face a legal hurdle in proving libel or defamation, which would require her to show that Mr. Tarpley published his post with malice or willful disregard of the truth. Her lawyer’s allegation in court papers, that the injuries to her reputation “are estimated at $150 million,” is preposterous; in fact, the lawsuit has probably done more to spread the fake news than the original blog post did.