Mrs. Rose O’Neal Greenhow, later-admitted Reb spy, was placed under house arrest in August 1861. The Yankee detectives made themselves quite at home in her house, drinking her brandy and keeping a watchful eye on the southern belle. Her books and papers were thoroughly searched, but the sly Rose Greenhow managed nonetheless to dispose of her most crucial documents right under the noses of the blundering Yankees. (Background: “Reb Spy Admits Link to ‘Cunning Calhoun'”, Ersjdamoo’s Blog entry of June 10, 2014.)
One of the documents seized by the Yankees was a paper dealing with the attempted poisoning of former-President James Buchanan. Mrs. Greenhow claims this paper was “a full and detailed account, so far as could be collected, of the appalling attempt of the Abolition party [Republican party] to poison President Buchanan, and the chiefs of the Democratic party, in Washington, at the National Hotel, a few days prior to the inauguration of President Buchanan.” 
This would have been in 1857, when Millard Fillmore unfortunately had lost his bid for president as the candidate of the “Know Nothings.” Instead of our Millard, the dotard Buchanan was elected. Buchanan went on to hobble the Union and left Abey Lincoln to inherit a big mess. 
The attempted poisoning of James Buchanan became known as the “National Hotel Disease.” The New York Times of June 5, 1857 reported, “A feeling of intense dissatisfaction pervades the public mind in the manner in which the mystery of the National Hotel Disease has been treated by the authorities of the City of Washington. From every quarter of the country come in denunciations of what is styled… the determination on the part of interested parties to stifle inquiry and hoodwink suspicion concerning what has every appearance of being the most gigantic and startling crime of the age.”
“Whatever it was, disease or poisoning, its effects were ‘chronic and debilitating.’ Deaths occurred ‘after months, and even years. The roll of the deceased included Mississippi Congressman John Quitman (1799 – 1858), Pennsylvania Congressman John G. Montgomery (1805 – 1857), and David Robison (1815 – 1859).'” 
Mrs. Greenhow claims that a Judge Black, the Attorney-General of the United States, under Mr. Buchanan, “told me also that he had obtained a clue to the whole plot, but that Mr. Buchanan would not allow the affair to be pursued, because of the startling facts it would lay open to the world, and that he shrank from the terrible exposure.” 
But did President Buchanan also shrink from any further potential invitations to the National Hotel?
Mrs. Greenhow faults Judge Black’s and President Buchanan’s discretion in the matter of the “National Hotel Disease”, claiming exposure of the conspiracy “might have averted the John Brown raid, and many other acts of the ‘Irrepressible Conflict’ party [Republican party].”
Because of after-effects of the “National Hotel Disease”, President James Buchanan “was for a long time in a very critical condition, and it was only by the use of powerful stimulants that his constitution rallied from the effects of the poison.”  Already a feeble man, Buchanan’s presidency was further weakened by the consequences of the apparent poisoning.
(The above first appeared at my Melchizedek Communique web site on May 11, 2011.)
——- Notes ——-
 Greenhow, Rose. My Imprisonment and the First Year of Abolition Rule at Washington.
London: Richard Bentley (publisher), 1863
 Redman, Brian. What Would Millard Do?. 2009. Published by Lulu.com. Also available as a Kindle e-book.