Presbyterianism is a form of church government, which is governed by representative assemblies of elders. When capitalized, Presbyterianism also refers to churches formed after the Reformation that trace their roots to the Church of Scotland. Presbyterian churches typically emphasize the sovereignty of God and the authority of the Bible. Some of the Presbyterian traditions can be traced to John Calvin. James Mill (the father of John Stuart Mill) was educated in the creed of Scottish Presbyterianism. And it is possible that Mill's ideas of representative democracy and universal suffrage were influenced by Prebysterian traditions: Prebysterianism prefers representative assemblies over absolute autocracy; the belief in the authority of the Bible (a written, objective entity) is also democratic in nature--it suggests that individuals are entitled to make interpretations of the Scriptures, instead of blindly submitting to religious authorities that can otherwise monopolize the interpretation. The church as a whole also values communal understanding of theology over individual understanding, which is another sign of democracy.
Sources:
https://www.churchofscotland.org.uk/__data/assets/pdf_file/0006/38787/O…
https://artuk.org/discover/artworks/presbyterian-catechising-210521