Popish Plot, an alleged Catholic conspiracy. In 1678 Titus Oates claimed he had uncovered a plot to murder King Charles II of England and replace him with James, his Roman Catholic brother. Nonconformists rushed to support the Anglican Whigs, who consequently won a great majority in the House of Commons. In 1679 the Whigs passed the "Exclusion Bill" to keep James from the throne, but the act failed to pass the House of Lords. It later developed that Oates had lied, and Whig popularity declined after capitalising on near-civil-war. Wikipedia