While Vane and Bradshaw might represent the Republicans or Commonwealth's men generally, the head of the Fifth-Monarchy Republicans was Harrison.

The Harrisonian Republic, the impassioned dream of this really great-hearted soldier, was the coming Reign of Christ on Earth, and the trampling down, in anticipation of that reign, of all dignities, institutions, ministries, and magistracies, that might be inconsistent with it.

In the Barebones Parliament, where the Fifth-Monarchy Men had been numerous, and where Harrison had led them, they had gone far, as we know, in conjunction with the Anabaptists, in a practical attempt to convert Cromwell's interim Dictatorship, with Cromwell's assent or acquiescence, into a beginning of the great new era.

They had voted down Tithes, Church-Establishments, and all their connexions, and only the steadiness of Rons, Sydenham, and the other sober spirits, in making that vote the occasion of a resurrender of all power into Cromwell's hands, had prevented the consequences.

And so, Cromwell's Protectorate having come in where Harrison wanted to keep a vacuum for the Fifth Monarchy, and that Protectorate having not only conserved Tithes and an Established Church, but professed them to be parts of its very basis, Harrison had abjured Cromwell for ever.
"Those who had been to me as the apple of my eye," said Harrison afterwards, "when they had turned aside, said to me, Sit thou on my right hand; but I loathed it." Through the Protectorate, accordingly, Harrison, dismissed from the Army, had been living as a suspected person, with great powers of harm; and, three or four times, when there were Republican risings, or threatenings of such, it had been thought necessary to question him, or put him under temporary arrest.
The last occasion had been just before the opening of the present Parliament, when he was arrested with Vane, Rich, and others, and had the distinction of being sent as far off as Pendennis Castle in Cornwall, while Vane was sent only to the Isle of Wight, and Rich only to Windsor.