During the Exclusion Crisis, Shaftesbury headed the movement to bar the Catholic heir, James II, from the royal succession, which is often seen as the origin of the Whig party.

Like many English Protestants of the period, Shaftesbury saw Catholicism as closely linked to "arbitrary government", and thus the prospect of a Catholic monarch as a threat to the rule of Parliament.

[2] Cooper's father was created a baronet in 1622, and he represented Poole in the parliaments of 1625 and 1628, supporting the attack on Richard Neile, Bishop of Winchester, for his Arminian tendencies.

In the following year his father remarried, this time to the widowed Mary Moryson, one of the daughters of wealthy London textile merchant Baptist Hicks and co-heir of his fortune.

[2] Cooper matriculated at Exeter College, Oxford, on 24 March 1637, aged 15,[3] where he studied under its master, the Regius Professor of Divinity, John Prideaux, a Calvinist with vehemently anti-Arminian tendencies.

[2] In October 1640, with opinion in the country swinging against the king's supporters (including Coventry), Cooper was not asked to stand for election for Tewkesbury in the Long Parliament.

[2] He contested, and by some accounts, won a by-election to the seat of Downton in Wiltshire, but Denzil Holles, soon to rise to prominence as a leader of the opposition to the King and a personal rival of Sir Anthony, blocked Cooper's admission to the Parliament.

[5] On 14 July, Cromwell appointed Cooper to the English Council of State, where he was a member of the Committee for the Business of the Law, which was intended to continue the reform work of the Hale Commission.

[2] In August 1659, Cooper was arrested for complicity in Sir George Booth's Presbyterian royalist uprising in Cheshire, but in September the Council found him not guilty of any involvement.

In the latter half of 1662, Ashley joined Sir Henry Bennet, the Earl of Bristol, and Lord Robartes in urging Charles to dispense peaceable Protestant Nonconformists and loyal Catholics from the Act of Uniformity.

[2] Ashley and his assistant John Locke drafted a plan for the colony known as the Grand Model, which included the Fundamental Constitutions of Carolina and a framework for settlement and development.

[2] The failures of the English during the Second Anglo-Dutch War led Charles II to lose faith in the Earl of Clarendon, who was dismissed as Lord Chancellor on 31 August 1667.

[2] Nevertheless, Ashley joined Arlington and Buckingham, as well as John Wilkins, Bishop of Chester, in introducing government-backed bills in October 1667 and February 1668 to include moderate dissenters within the Church of England.

Under the terms of the Secret Treaty of Dover, Charles would receive an annual subsidy from France (to enable him to govern without calling a parliament) in exchange for a promise that he would convert to Catholicism and re-Catholicize England at an unspecified future date.

[2] In an attempt to conciliate the Nonconformists, on 15 March 1672, Charles II issued his Royal Declaration of Indulgence, suspending the penal laws that punished non-attendance at Church of England services.

[8] As Lord Chancellor, he addressed the opening of a new session of the Cavalier Parliament on 4 February 1673, calling on parliament to vote funds sufficient to carry out the war, arguing that the Dutch were the enemy of the monarchy and England's only major trade rival, and therefore had to be destroyed (at one point he exclaimed "Delenda est Carthago"); defending the Great Stop of the Exchequer; and arguing in support of the Royal Declaration of Indulgence.

[2] Shaftesbury, Arlington, James Butler, 1st Duke of Ormonde, and Henry Coventry all urged Charles II to divorce Catherine of Braganza and remarry a Protestant princess.

[2] He coordinated his efforts with a group of other peers who were displeased with the possibility of a Catholic succession; this group met at the home of Denzil Holles, 1st Baron Holles, and included Charles Howard, 1st Earl of Carlisle, Thomas Belasyse, 2nd Viscount Fauconberg, James Cecil, 3rd Earl of Salisbury, George Villiers, 2nd Duke of Buckingham, and George Savile, 1st Viscount Halifax.

[2] In late April 1675, Danby introduced a Test Oath by which all holding office or seats in either House of Parliament were to declare resistance to the royal power a crime, and promise to abstain from all attempts to alter the government of either church or state.

[2] Shaftesbury led the parliamentary opposition to Danby's Test Bill, arguing that, under certain circumstances, it was lawful to resist the king's ministers, and that, as in the case of the Protestant Reformation, it was sometimes necessary to alter the church so as to restore it.

[2] He supported the Test Act 1678, which required that all peers and members of the House of Commons should make a declaration against transubstantiation, invocation of saints, and the sacrifice of the mass, effectively excluding all Catholics from Parliament.

[2] He also drafted a pamphlet that was never published, entitled "The Present State of the Kingdom": in this pamphlet, Shaftesbury expressed concern about the power of France, the Popish Plot, and the bad influence exerted on the king by Danby, the royal mistress Louise de Kérouaille, Duchess of Portsmouth (a Catholic), and the Duke of York, who according to Shaftesbury was now attempting "to introduce a military and arbitrary government in his brother's time".

[2] Shaftesbury attempted to neutralise the influence of the episcopal bench in favour of Danby by introducing a bill moving that the bishops should not be able to sit in the House of Lords during capital trials.

[2] On 21 August 1679, the king fell ill, leading Essex and Halifax (who feared Monmouth was about to launch a coup) to ask the Duke of York, whom Charles had sent to Brussels in late 1678, to return to England.

[2] On 26 June 1680, Shaftesbury led a group of fifteen peers and commoners who presented an indictment to the Middlesex grand jury in Westminster Hall, charging the Duke of York with being a popish recusant in violation of the penal laws.

[2] On 23 December 1680, Shaftesbury gave another fiery pro-Exclusion speech in the Lords, in the course of which he attacked the Duke of York, expressed mistrust of Charles II, and urged the parliament to not approve any taxes until "the King shall satisfie the People, that what we give is not to make us Slaves and Papists".

[2] At the Oxford Parliament, Charles insisted he would listen to any reasonable expedient short of changing the line of succession that would assuage the nation's concerns about a Catholic successor.

[2] On 24 March 1681, Shaftesbury announced in the House of Lords that he had received an anonymous letter suggesting that the king's condition could be met if he were to declare the Duke of Monmouth legitimate.

[2] The only issue the Oxford Parliament had resolved had been the case of Edward Fitzharris, who was to be left to the common law, although Shaftesbury and 19 other peers signed a formal protest of this result.

[2] This, combined with the fact that the jury was handpicked by the Whig Sheriff of London, meant the government had little chance of securing a conviction and on 13 February 1682, the case against Shaftesbury was dropped.