Churchill was returned as Member of Parliament for Weymouth and Melcombe Regis in a contest at the first general election of 1701 and was blacklisted for opposing preparations for war with France. He was returned unopposed in the second general election of 1701 and supported Harley for the Speaker in January 1702, He supported the motion on 26 February 1702 to vindicate the Commons' proceedings in impeaching William's Whig ministers. In 1702, he became a lieutenant-general, at the same time receiving the colonelcy of the Coldstream Regiment of Foot Guards. He was returned unopposed as MP for Weymouth at the 1702 English general election. At Blenheim in 1704, he served under his elder brother John Churchill, 1st Duke of Marlborough, and commanded the center of the allied line. During the March to the Danube he oversaw the artillery and infantry contingents. He was returned in a contest for Weymouth at the 1705 English general election. He supported the Court in the proceedings on the 'place clause' of the regency bill on 18 February 1706. At the battle of Ramillies, again serving under his brother, he ordered four brigades of foot to attack the village. He resigned his Lieutenancy of the Tower in 1706, and he served as Governor of Guernsey from 1706 to 1711. In 1707, he was made a full general. In late March 1708 onwards Churchill was 'seized with an apoplectic fit' but was non-the less returned as MP for Weymouth at the 1708 British general election. He suffered ongoing ill-health and began to drink heavily, and did not stand for Weymouth at the 1710 British general election.