Donnelly's work corresponds to the writings of late-19th and early-20th century figures such as Helena Blavatsky, Rudolf Steiner, and James Churchward.

In 1855, he resigned his clerkship, entered politics with campaign speeches for Democratic candidates, and participated in communal home building schemes.

[1] Donnelly moved to the Minnesota Territory in 1857 amidst rumors of a financial scandal, and there he settled in Dakota County.

Though he was not elected, Donnelly was recognized as a highly effective political speaker, which led to a successful campaign for lieutenant governor, which he held from 1860 to 1863.

The document of 12 short paragraphs, as altered slightly for the party's first nominating convention in Omaha that July, was the pithiest and soon became the most widely circulated statement of the Populist credo.

[5] Donnelly talked about the corruption of politics and voting, newspapers giving out false and biased material, and how the Populists needed to take back the country that was their own.

The book sold well and is widely credited with initiating the theme of Atlantis as an antediluvian civilization that became such a feature of popular literature during the 20th century and contributed to the emergence of Mayanism.

Donnelly suggested that Atlantis, whose story was told by Plato in the dialogues of Timaeus and Critias, had been destroyed during the same event remembered in the Bible as the Great Flood.

In 1888, he published The Great Cryptogram in which he proposed that Shakespeare's plays had been written by Francis Bacon, an idea that was popular during the late 19th and early 20th century.

He then traveled to England to arrange the English publication of his book by Sampson Low, speaking at the Oxford (and Cambridge) Union in which his thesis "Resolved, that the works of William Shakespeare were composed by Francis Bacon" was put to an unsuccessful vote.

The People's Party was a development of the National Farmers' Alliance, and had a platform that demanded the abandonment of the gold standard and later for the adoption of free silver, the abolition of national banks, a graduated income tax, a direct election of senators, civil service reform, and an eight-hour day.

"[12] However, Donnelly's concept of "hyperdiffusionism," which purports to detect prehistoric catastrophes in the mythologies of multiple unrelated cultures, is credited as inspiring J. R. R. Tolkien's fictional Númenor.