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Consensus supports three different voting systems, each designed for specific election scenarios. Choose the system that best matches your election requirements.

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Supported Voting Systems

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First Past The Post (FPTP)

The simplest voting system where voters select a single candidate. The candidate with the most votes wins.

Best for

  • Simple yes/no decisions
  • Elections with a clear frontrunner
  • Quick decision-making processes
  • Voters unfamiliar with ranked voting
How it works:
  • Each voter selects one candidate
  • Votes are tallied
  • The candidate with the highest vote count wins
  • No majority required (plurality wins)
FPTP can result in ties if multiple candidates receive the same highest vote count. The system will flag tied candidates for manual resolution.
Implementation details: 
// From src/services/strategies/FPTPStrategy.ts:56-58
validateBallot(ballot: Ballot, _candidateCount: number): boolean {
    // FPTP requires single candidate selection
    return ballot.preferences && ballot.preferences.length === 1;
}

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Single Transferable Vote (STV)

A ranked-choice system that ensures winners meet a quota threshold through preference redistribution.

Best for

  • Multi-winner elections (council seats, board positions)
  • Ensuring proportional representation
  • Reducing vote wastage
  • Complex organizational decisions
How it works:
  1. Voters rank candidates in order of preference
  2. A quota is calculated: (Total Votes / 2) + 1 (Droop quota)
  3. First preference votes are counted
  4. If no candidate meets the quota:
    • The candidate with the fewest votes is eliminated
    • Their votes are redistributed to voters’ next preferences
  5. Process continues until a winner meets the quota
Consensus implements a simplified single-winner STV. In production scenarios, STV is typically used for multi-winner elections with more complex redistribution rules.
Ballot validation: 
// From src/services/strategies/STVStrategy.ts:90-99
validateBallot(ballot: Ballot, _candidateCount: number): boolean {
    // STV requires ranked preferences
    if (!ballot.preferences || ballot.preferences.length === 0) {
        return false;
    }

    // Check for duplicates - each candidate can only be ranked once
    const uniquePreferences = new Set(ballot.preferences);
    return uniquePreferences.size === ballot.preferences.length;
}

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Alternative Vote (AV)

Also known as Instant Runoff Voting, AV ensures the winner has majority support through elimination rounds.

Best for

  • Single-winner elections requiring majority support
  • Presidential or leadership positions
  • Reducing strategic voting
  • Elections with multiple strong candidates
How it works:
  1. Voters rank candidates in order of preference
  2. Majority threshold: (Total Votes / 2) + 1
  3. First preferences counted
  4. If no candidate has a majority:
    • Candidate with fewest votes is eliminated
    • Their ballots transfer to voters’ next active preference
    • Process repeats until a candidate reaches majority
  5. If only one candidate remains, they win by default
Key differences from STV:
  • Requires majority (50%+1) not just quota
  • Continues until absolute majority achieved
  • Better suited for single-winner scenarios
// From src/services/strategies/AVStrategy.ts:6-8
calculateResults(ballots: Ballot[], candidates: Candidate[]): VoteResult[] {
    const totalVotes = ballots.length;
    const majority = Math.floor(totalVotes / 2) + 1;
    // ... elimination rounds continue until majority found
}

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Comparing Voting Systems

FPTP

Complexity: Simple
Winner needs: Plurality
Ballot: Single choice
Best for: Quick decisions

STV

Complexity: Moderate
Winner needs: Quota
Ballot: Ranked preferences
Best for: Proportional representation

AV

Complexity: Moderate
Winner needs: Majority
Ballot: Ranked preferences
Best for: Majority mandate

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Selecting a Voting System

When creating an election, choose your voting system based on: 
// From src/domain/enums/index.ts:1-6
export enum ElectionType {
    FPTP = "FPTP", // First Past The Post
    STV = "STV",   // Single Transferable Vote
    AV = "AV",     // Alternative Vote
    PREFERENTIAL = "PREFERENTIAL", // Alias for STV
}
1

Assess your requirements

Determine if you need plurality, quota, or majority support for your winner
2

Consider voter familiarity

If voters are unfamiliar with ranked voting, FPTP may be more appropriate
3

Evaluate time constraints

FPTP provides fastest results; ranked systems may require more processing
4

Set voting system

Configure the system when creating your election - it cannot be changed once the election is activated
The voting system cannot be changed after an election is activated. Choose carefully during the draft phase.

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Next Steps

Election Management

Learn how to create and manage elections

Results Calculation

Understand how results are calculated for each system

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