Most of his supporters were originally followers of the Duke of Newcastle, but from the mid-1760s they transferred their allegiance to Rockingham. While Prime Minister (1765–66), his government repealed the American Stamp Act and the controversial cider excise. He and his supporters strenuously opposed Lord North and the American War of Independence and argued for financial reforms, which the second Rockingham administration undertook in 1782. On his death in office the Rockingham Whigs split into further factions, of which the most important formed the basis of the new Whig party which was evolving at the end of the 18th century.