The Exclusion Crisis ran from 1679 until 1681 in the reign of King Charles II of England, Scotland and Ireland. Three Exclusion bills sought to exclude the King's brother and heir presumptive, James, Duke of York, from the thrones of England, Scotland and Ireland because he was Catholic. None became law. Two new parties formed. The Tories were opposed to this exclusion while the "Country Party", who were soon to be called the Whigs, supported it. While the matter of James's exclusion was not decided in Parliament during Charles's reign, it would come to a head only three years after James took the throne, when he was deposed in the Glorious Revolution of 1688. Finally, the Act of Settlement 1701 decided definitively that Catholics were to be excluded from the English, Scottish and Irish thrones, now the British throne.
In 1673, when the Duke of York refused to take the oath prescribed by the new Test Act, it became publicly known that he was a Roman Catholic. In the five years that followed, growing concern regarding the shift towards the king and court's pro-French stance and perceived emulation of its Catholicism and arbitrary ('absolute') behaviour, led to growing opposition amongst some politicians and peers in Parliament. Between 1675 and 1678, the First Earl of Shaftesbury for example, highlighted in print and in the House of Lords the dangers of arbitrary government and Catholicism to Parliament, the nation, the rule of law, and English rights and liberties. This feat was exacerbated by the promulgation of the Duke of York's Catholicism and the Secret Treaty of Dover (1670).
In 1678, the Duke of York's secretary, Edward Colman, was named by Titus Oates during the Popish Plot as a conspirator to subvert the kingdom. Members of the Anglican English establishment could see that, in France, a Catholic king was ruling in an absolutist way, and a movement gathered strength to avoid such a form of monarchy from developing in England, as many feared it would if James were to succeed his brother Charles, who had no legitimate children.