This is the newest form of polity but is also perhaps the most influential on the American church as the various Puritan and non-conformist churches that struggled to gain authority in Europe flourished and grew in the United States.
The rise of political democracy contributed to and benefited from the corresponding rise of Congregationalism. I suspect the majority of people in Evangelical churches, and certainly within the Antioch movement, have roots within a Congregationalist church—whether Baptist, Church of Christ, etc.
In a Congregationalist church, membership is extremely important because members hold authority over the church. Most churches will delegate the authority to a lead pastor and staff, but still gather to make to vote on major decisions as a full membership. More rarely, some churches require a member vote on virtually all decisions.
Pastors lead the vision of the church but must do so with the support of the members of the church. Powerful members can hold equal, if not more authority than the lead pastor, and this can extend for generations.
Some churches have a very active membership, with consistent business meetings to approve minor decisions and committees to oversee most elements of church life. Others delegate most of the authority to the staff that they’ve hired.
Advocates of the Congregational model point to Jesus’ teaching in Matthew 18 regarding conflict and discipline. The final stage of conflict involves the offender to be taken before the whole church—not the bishop nor the elders. Likewise, Paul confronted the Corinthian church as a whole for tolerating sin, not just the leadership. The letters in Revelation are similarly addressed to the whole church in each city.
In Act 6:3 it appears that the church chose the deacons (though the apostles commissioned them). Acts 15:22 is a fascinating verse that includes everyone: apostles, elders, and the whole church in the decision to spread guidance regarding the Gentiles and could be used to “prove” all three models.
The Congregational model leads to deep ownership in the church. People feel it is their church and recognize their responsibility to be a priest and minister to others. Historically, it’s also been a bulwark against liberal theology. The Baptist movement is perhaps the longest lasting church movement in history; it’s been marked by splits, but these have created space for a strong, Evangelistic remnant to preach the Word boldly even when other churches slowly abandoned the faith since no one person holds the authority to lead astray. Lastly, the model is a constant reminder of the priesthood of the believer. If the whole church doesn’t assume responsibility, then there is no church.
In a word: politics. The advocates of Congregationalism speak of churches in which each member seeks God diligently and then gather together to vote, based on the fruit of corporate discernment. This is a noble aspiration but rarely is it realized.
In most instances, political groups form within the church with virtually no mechanism to ensure Godly men and women hold the authority. Backstabbing, gossiping, rumors, and slander are a tragic reality when politics are introduced into church life.
Additionally, apostolic momentum is severely limited. By nature, visionaries cause change, and change causes friction. When a leader creates waves then people will react to change, often negatively. Often congregational decisions are made simply to maintain the status quo and comfort. Vision becomes replaced by a commitment to the status quo. In summary, I believe empowering the church to live on mission should always be a core concern, but I’m not convinced Congregationalism is the best way to facilitate this. At the same time, I see the danger of a church model that fails to involve the congregation in its decision-making.