He was the heir of a Puritan family.  His father, Sir Edward Harley, had been conspicuous among the patriots of the Long parliament, had commanded a regiment under Essex, had, after the Restoration, been an active opponent of the Court, had supported the Exclusion Bill, had harboured dissenting preachers, had frequented meetinghouses, and had made himself so obnoxious to the ruling powers that at the time of the Western Insurrection, he had been placed under arrest, and his house had been searched for arms.  When the Dutch army was marching from Torbay towards London, he and his eldest son Robert declared for the Prince of Orange and a free Parliament, raised a large body of horse, took possession of Worcester, and evinced their zeal against Popery by publicly breaking to pieces, in the High Street of that city, a piece of sculpture which to rigid precisians seemed idolatrous.  Soon after the Convention became a Parliament, Robert Harley was sent up to Westminster as member for a Cornish borough.  His conduct was such as might have been expected from his birth and education.  He was a Whig, and indeed an intolerant and vindictive Whig.  Nothing would satisfy him but a general proscription of the Tories.  His name appears in the list of those members who voted for the Sacheverell clause; and, at the general election which took place in the spring of 1690, the party which he had persecuted made great exertions to keep him out of the House of Commons.  A cry was raised that the Harleys were mortal enemies of the Church; and this cry produced so much effect that it was with difficulty that any of them could obtain a seat.  Such was the commencement of the public life of a man whose name, a quarter of a century later, was inseparably coupled with the High Church in the acclamations of Jacobite mobs.482

Soon, however, it began to be observed that in every division Harley was in the company of those gentlemen who held his political opinions in abhorrence; nor was this strange; for he affected the character of a Whig of the old pattern; and before the Revolution it had always been supposed that a Whig was a person who watched with jealousy every exertion of the prerogative, who was slow to loose the strings of the public purse, and who was extreme to mark the faults of the ministers of the Crown.  Such a Whig Harley still professed to be.  He did not admit that the recent change of dynasty had made any change in the duties of a representative of the people.  The new government ought to be observed as suspiciously, checked as severely, and supplied as sparingly as the old one.  Acting on these principles he necessarily found himself acting with men whose principles were diametrically opposed to his.  He liked to thwart the King; they liked to thwart the usurper; the consequence was that, whenever there was an opportunity of thwarting William, the Roundhead stayed in the House or went into the lobby in company with the whole crowd of Cavaliers.