Long was known for his moderate stance in politics, which was also demonstrated in parliament, following his election to the Long Parliament as a recruiter MP for Wells (1645–53). He voiced his strong opposition to Pride's Purge (6 December 1648), and on the day following the purge, he acted as a teller on a critical vote. After a few occasional appearances, he eventually absented himself from the House of Commons in protest. He became a conformist by taking his dissent and resuming his seat in the Rump Parliament, although he played no part in the trial and execution of Charles I. From that point on he played an active role in the work of committees, his moderating influence reflected in government policies.