The Illuminati Scare refers to the public accusation, made by prominent New England conservatives in the late 1700s, that the Bavarian Illuminati were responsible for domestic opposition to Federalist policies. This accusation surfaced in numerous sermons, orations, and newspapers from 1798 to 1799, amid high domestic tensions over the Quasi-War with France, the Alien and Sedition Acts, and the status of the church in New England. Relying on the conspiracy theories of John Robison, Federalist clergymen and polemicists attempted to tarnish the Democratic-Republicans by associating them with a secretive revolutionary order, supposedly bent on overthrowing all governments and destroying Christianity. The Illuminati scare has continued to interest historians due to its resemblance to McCarthyism and other similar phenomena in American history. 
The Scare may be seen as the apogee of the factionalism and distrust that characterized American politics in the 1790s. Although it has struck modern observers as an example of either hysteria or demagoguery, distrust of political opponents and accusations of treason were common at the time. After the Jay Treaty, Democratic-Republican leaders such as Thomas Jefferson and James Madison regularly accused the Federalists of being pro-British, referring to them as “monarchists” or as “the English Party.” The Federalists, similarly, attacked the Democratic-Republicans as unpatriotic because of their perceived involvement with the Whiskey Rebellion, the mission of Citizen Genet, and the Democratic Societies, and because of their continued support for France after the Terror and the French depredations on American ships. Federalist leaders denounced the opposition as treacherous, as Jacobins, or as “Frenchmen in their feelings and wishes.”In addition, religious conservatives were alarmed by the circulation of Deist ideas and by a perceived increase in irreligion. Despite widespread public hostility toward France in the wake of the XYZ Affair, Democratic-Republican criticism of John Adams and the Federalists continued throughout the naval war. In this context, Robison’s Proofs of a Conspiracy… seemed to provide conservatives with potent ammunition to discredit their political rivals.
In the short term, the Illuminati scare resulted in embarrassment for Morse and others, as they repeatedly failed to provide convincing evidence in support of their claims. Some have claimed that the backlash against the Scare was a near-fatal blow to the Federalists, who lost power at the federal level in 1800, never to get it back, and also a blow to the clergy and the establishment of the church throughout New England. Others have suggested that the Scare gave rise to the “evangelistic culture of the early nineteenth century,” as the clergy saw the need to launch a counteroffensive against the supposed foes of religion. The Scare may also have contributed to later conspiracy theories involving Masons, and to the popularity of Illuminati-themed conspiracy theories down to the present.
From Wikipedia – the Free Encyclopedia