Compare Top Two and STAR Voting

Two round Runoff Voting has been used for hundreds of years, all around the world. It's used in California, Louisiana, and Washington as a replacement for the partisan primary / general election system statewide, and in many other states for local elections. In an Open Primary 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 and other options? At Equal Vote we evaluate voting systems according to five primary criteria: Equality, Honesty, Accuracy, Simplicity, and Expressiveness. The narrative below describes and then compares Top Two and STAR Voting according to these five metrics.


Does the voting system provide an equal weight vote and 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 full equality to voters

STAR Voting passes the test of balance which that tells us definitively that it provides an equal vote to all the voters. If an election was tied before I voted, you can always cast an opposite vote that would bring the election back to a tie. With STAR Voting this is always possible, and this test of equality is passed both in the scoring round and in the runoff. 

Top Two only provides equality in the runoff

In Top Two, the runoff vote is always equal. Vote-splitting is impossible if there are only two candidates in the race. But what about the first stage? Because the voter is limited to just a single choice between many candidates in the first stage, and because the Top Two system puts all the candidates together into one big primary it actually magnifies the vote-splitting spoiler effect when compared to the party-segregated closed primary system. Choose One elections are less accurate the more candidates you have in the race. Six_candidates.jpg

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 elections simply push the spoiler effect inequality into the primary vote.


Can the voter safely express an honest opinion on the ballot, and likewise, to what level does the system incentivize voters to vote strategically?

In Top Two, voters can't always safely vote for their favorite candidates in the primary

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.

STAR Voting 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.


How accurately does the voting system reflect the will of the people?

Top Two is somewhat better 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, Ranked Choice Voting (RCV), and Score+Top Two (which formed the basis for the early analysis of STAR Voting). Like the more contemporary VSE simulations, Smith found RCV 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 Ranked Choice Voting.

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, STAR Voting is "unquestionably a top-shelf method."


How easy is the system for voters to understand and cast ballots, and how easy is it for elections officials to tabulate results, hand-recount, and conduct audits?

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 ubiquitous 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 representative results in a single election than Top Two manages in multiple votes, STAR Voting is considerably simpler to administer overall.


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, STAR Voting allows the voter to express, and counts, a nuanced level of support for any number of candidates on the ballot.

Upgrading Top-Two

The simplest way to make a top two system dramatically better 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. The system is is also known as Approval Voting with a top two runoff, or the Unified Primary. 

In this version of the Top Two 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!”

Since they know that the top two advance, they benefit by supporting at least two: one or more favorite(s) and, if necessary, a merely acceptable candidate too. Instead of choosing the lesser of two evils in the general election, the voters may be able to select the more awesome of two greats. And unlike many other primary election systems, it's always safe to vote for your honest favorite. 

See how Top Two and the Approval + Top Two stack up in the overall discussion of Voting Science.


The Takeaway

To sum things up, Top Two Runoff elections are a real step up. They provide a significant upgrade over a Choose-One Plurality primary and general election, they eliminate vote-splitting and the Spoilers Effect in the election that matters most, and they get results almost on par with Ranked Choice Voting, without the cost and complexity. They also allow voters and candidates from all political parties, and non-affiliated voters, to participate on a level playing field. 

That said, we can do even better. Simply upgrading the voting method used from Choose One to Approval Voting takes this from a middle of the road system to a top tier one, and for those who want to go even farther, eliminating the need for a second election entirely and unlocking even more accurate results, STAR Voting takes us the rest of the way there. STAR Voting is able to be so accurate and resilient against strategic voting because it includes a top two runoff. In STAR Voting the two highest scoring candidates advance to an automatic runoff, and each voter's vote goes to the finalist they preferred.