The Top Two
Two round Runoff Voting has been used for hundreds of years in many different locales around the world, and is used in Oregon currently for non-partisan races, as well as in California and Washington as a replacement for the partisan primary / general election system used in many other states. In a top two runoff system, all of the candidates compete in an open first round. Voters choose a single favorite, and the two highest vote-getters advance to a second runoff election where all the voters get to choose between them.
Metrics For Comparison
How does the Top Two system stack up against STAR Voting? Equal.Vote evaluates voting systems according to five primary criteria: equality, honesty, accuracy, simplicity, and expressiveness. The narrative below describes and then compares Top Two and SRV according to these five metrics.
Equality: Does the voting system provide an equal weight vote and thereby comply with the fundamental principle of 'One Person, One Vote'?
The U.S. Supreme Court has found unequivocally that 'One Person, One Vote' requires that "each vote be given as much weight as any other vote." Put simply, our very notion of democracy requires that the voters and the candidates are on an even playing field in every election, and every proposed reform should be scrutinized through this lens.
STAR Voting provides equality to voters
STAR Voting passes the test of balance that tells us definitively that a voting system provides an equal weight vote to all the voters. With STAR Voting, every possible vote expression in both the scoring and automatic runoff stages has an equal, balancing expression, and all the voters' expressions about all the candidates are counted.
Top Two only provides equality in the runoff
The vote between the top two is always equal. But what about the first stage? Because the voter is limited to just a single choice between many candidates in the first stage, it actually magnifies the vote-splitting spoiler effect when compared to the party-segregated closed primary system.
As a result, Californians, who now use Top Two instead of a closed primary, have experienced directly the pernicious effects of increased vote-splitting: campaign costs have increased and in some cases two candidates advance who don’t at all represent the majority. Fundamentally, California's top two simply pushes the spoiler effect inequality into the primary vote.
Honesty: Can the voter safely express her honest opinion on the ballot, and likewise, to what level does the system disincentivize voters from strategically voting insincerely in order to produce a better outcome?
Voters in Top Two often can't safely vote for their favorite candidates
Because it is a plurality vote, Top Two heavily incentivizes "Lesser Evil" voting in the first stage: the voter must consider not just which candidate he prefers, but which one stands the best shot of beating the candidate the voter fears most.
SRV promotes honest voting
STAR Voting's scoring phase ensures that the two strongest candidates overall advance to the final runoff, and the runoff phase reduces the incentive to score second choices tactically. With STAR Voting, you can honestly support your true favorite and second choice without worrying you'll be promoting a losing candidate over a stronger consensus choice or unduly harming your favorite's chance of winning.
Accuracy: How accurately does the voting system reflect the will of the people?
Top Two is mediocre, at best, in terms of representation accuracy
Voting method simulation is used primarily to determine how accurately a voting method will produce an outcome that represents the will of the electorate. In a real human election it's hard to actually know what the voters really wanted - they could have been voting strategically, exit polling is imprecise and so on. By running simulated voters through thousands or millions of simulated elections, voting systems can be concretely evaluated and compared.
In the early 2000's, Princeton Math Ph.D. Warren Smith evaluated dozens of voting methods including Top Two, IRV and Score+Top Two (which formed the basis for the early analysis of STAR Voting). Like the more contemporary VSE simulations, Smith found IRV to be mediocre in terms of representative accuracy, and Score+Top Two (STAR in the case of VSE) to be best-in-class. Notable is that Top Two performs at almost the same level of accuracy as IRV.
STAR Voting tops the list
STAR Voting simulates best-in-class in the several election method simulators that have included it. Across the board, with both honest voters and mixtures of strategic voters, SRV is "unquestionably a top-shelf method."
Simplicity: How easy is the system for voters to understand and cast ballots, and how easy is it for elections officials to tabulate and hand-recount?
While the counting mechanism for Top Two is incredibly simple, as it is the same plurality system that is in wide use today, the addition of a second election adds considerable complexity to an otherwise very simple system. That's a lot of extra cost for the state to administer, and voter turnout in the two elections differs, which can skew the results. Do you run the first phase before the general election date, in which fewer voters will participate in the stage that narrows the field? Or do you run the second phase after the general election date, in which case fewer voters will participate in the stage that actually chooses the winner?
STAR Voting, like plurality and Top Two, is precinct-summable, which makes it considerably simpler to administer than systems like Instant Runoff Voting that must be tabulated centrally. While the STAR Voting ballot is not typical of the voting experience, scoring is ubiquitious in our society, so we imagine an easy transition from the limit of one choice to the option to score any and all choices the voter desires. Finally, because STAR Voting is much more accurate at producing reprsentative results in a single election than Top Two manages in multiple votes, STAR Voting is considerably simpler to administer overall.
Expressiveness: Can the voter express a nuanced opinion on the outcome?
Ranking is more expressive than plurality
Our current voting system, where we are limited to picking a single favorite in each election, is the least expressive voting system humans have ever constructed. Instant Runoff Voting allows the voter to express an opinion on multiple candidates by placing them in preference order.
Preference order alone leaves out information
The same ordering A > B > C could mean that the voter thinks any of the following:
- A is an awesome candidate, B is mediocre and C is the devil incarnate
- A is awesome, B is almost as awesome, and C is just a hair less awesome than A and B
- A is above average, B is mediocre, and C is mediocre and dishonest
Furthermore while IRV lets you express support for more than one candidate, it doesn't actually count that secondary support at all until your first choice candidate is eliminated.
Scoring is more expressive than ranking
Instead of only counting the voter's support for one candidate at a time, SRV allows the voter to express, and counts, a nuanced level of support for any number of candidates on the ballot.
The Equal Top Two
The simplest way to make a top two system awesome and actually equal is to remove the single choice limitation in the first phase. That’s it. Instead of making one choice per office, voters get to look at each candidate individually.
In this version of the Top Two, also known as the Unified Primary, voters are able to honestly express support for candidates they actually prefer, without having to consider first who has the most financial strength or who the media says is “electable.” They can actually look at a candidate and think, “I like. Support!”
See how Top Two and the Equal Top Two stack up in the overall discussion of Voting Science.