In Pride's Purge, all members of parliament (including most of the political Presbyterians) who would not accept the need to bring the King to trial had been removed.
Thus the Rump never had more than two hundred members (less than half the number of the Commons in the original Long Parliament).
The Rump was created by Pride's Purge of those members of the Long Parliament who did not support the political position of the Grandees in the New Model Army.
Just before and after the execution of King Charles I on 30 January 1649, the Rump passed a number of acts of Parliament creating the legal basis for the republic.
The only force keeping it together was the personality of Oliver Cromwell, who exerted control through the military by way of the "Grandees", being the Major-Generals and other senior military leaders of the New Model Army.
Not only did Cromwell's regime crumble into near anarchy upon his death and the brief administration of his son, but the monarchy he overthrew was restored in 1660, and its first act was officially to erase all traces of any constitutional reforms of the Republican period.
Despite its unpopularity, the Rump was a link with the old constitution and helped to settle England down and make it secure after the biggest upheaval in its history.
By 1653, France and Spain had recognised England's new government.
They included: supporters of religious independents who did not want an established church and some of whom had sympathies with the Levellers; Presbyterians who were willing to countenance the trial and execution of the King; and later admissions, such as formerly excluded MPs who were prepared to denounce the Newport Treaty negotiations with the King.
Most Rumpers were gentry, though there was a higher proportion of lesser gentry and lawyers than in previous parliaments. This left the Rump as basically a conservative body whose vested interests in the existing land ownership and legal systems made it unlikely to want to reform them.