In his long political career he was a Member of Parliament for seventeen years and spearheaded the Whig opposition to King James II's government, which later developed the two party political system under Queen Anne. In 1689 he was sworn of the Privy Council and made Comptroller of the Household by King William III, establishing the link between the royal position and government for the first time.
He went out of office in 1702, after the accession of Anne (who disliked him), but in 1706, he was created Earl of Wharton and Viscount Winchendon in the Peerage of England. He served as Lord Lieutenant of Ireland 1708–1710.
Under George I of England, he returned to favor. In January 1715, he was created Marquess of Catherlough, Earl of Rathfarnham, and Baron Trim in the Peerage of Ireland, and in February 1715 Marquess of Wharton and Marquess of Malmesbury in the Peerage of Great Britain.