Consensus Voting
Voting systems which do not exhibit Independence of Clones require some way of narrowing down the field of candidates before voting begins. Often in the United States this takes the form of partisan primaries, separate elections held before the general election which select the candidate who competes. If the primary did not narrow the field, similar candidates would create a “spoiler effect” and would reduce their own chances of victory.
This has many downsides, and thus a voting system which could do away with primaries entirely because it does not exhibit the Spoiler Effect is preferable to one which requires primaries.
First, primaries are expensive – in terms of administrative costs, in terms of voter attention, and in terms of the costs of running a campaign. Administrators need to run and pay for two elections, not just one, and voters have to submit a ballot twice, and candidates have to campaign for twice as long. Over time, the one-time costs of switching to a new voting system could be recouped solely from money saved in not having to run primaries.
Second, primaries give a disporportionate voice to the extremes of each party in two ways. Primaries often have lower turnout than the general election, so those that do turn out tend to be more partisan [citation needed], and the candidate will need to tailor their appeal accordingly. And if the primary is partisan – wherein each political party has a separate primary, and voters can only vote in one – then to win, a candidate need only the support of the most extreme half of their party. If the distirict itself is partisan, often due to gerrymandering, then sometimes the primary determines the outcome of the general election, as the opposing candidate isn’t a realistic “moderating force.” This is harmful once the candidate gets into office; they have a disincentive to support initiatives that are broadly popular but are opposed by extremists in their party, becase doing so might lose them votes more votes from among the set of people who determine their primary outcome – and the much larger set of people who support the initiaive are structually prevented from rewarding the candidate to compensate. At its best this does at least serve the interests of the same-party extremists; this dynamic becomes toxic, though, when even the extremists support an initiative, but the candidate still doesn’t have an incentive to help the initiative succeed – because, with their extremist base, they can always successfuly blame “the other side” on the failure and still get re-elected.
Partisan primaries combined with partisan-leaning districts lead to a collapse of governance, because elected officials are no longer accountable to their constituents for the success or failure of the government when their electoral success is founded on the bloc most receptive to shifting the blame elsewhere.