I think they should be eliminated, or at least significantly reduced in numbers before the 2012 cycle begins.

They are essentially free agents, able to vote their conscience based on whatever criteria they choose. As a collective group, either they ratify the choice of the pledged delegates, in which case they're not needed, or (to borrow the Obama campaign's framing, back when he was trailing by over 100 SDs) they would "overturn the will of the people" as expressed by their duly elected pledged delegates, with the presumption being the latter action would clearly be undemocratic and unfair.

The present structure, where 20% of delegates are SDs, combines with the proportional nature of the caucuses and primaries to make it quite hard for any candidate to win an outright majority based only on pledged delegates in a tightly contested battle: you'd need to get 62% of the pledged delegates to secure the nomination. As Chuck Todd and other delegate counters have realized since Super Tuesday, that's quite difficult if both campaigns push on for the whole process.

And indeed here we are with two closely matched campaigns, neither of which can win a first-ballot nomination without a large block of SDs behind them.

I've heard it said that the SDs are a "safety valve", and/or that they can "save the party from itself". But I have a hard time envisioning a scenario where they might actually "save" anything. What circumstances could SDs decide en masse to back a candidate with fewer pledged delegates to "save" the party that wouldn't result in alienating the leading candidate and her or his supporters? I'm having a hard time seeing where they truly can help.

In a close election like this one, the presence of SDs who can vote their conscience, and change their mind, encourages a losing candidate to continue fighting a vigorous campaign longer, because he or she still has some hope of winning the nomination. Is this a net positive for the party's chances of winning in the fall? This year, even after all the voters have had their say, neither candidate will have the nomination assured without SD votes, so the contest continues as long as both sides want to keep going. And it's most likely to continue when two candidates are fairly evenly matched, potentially causing greater acrimony between sides, and hurting the chances for unity in the fall.

My other argument against SDs is that they skew the process from the outset. This could, I suppose, be called a feature, not a bug: we want presidential candidates who can garner support from party insiders for their campaigns. But insider support is valuable in other ways (contacts, fund raising, etc.) beyond simply a vote at the convention, and it seems to me giving these people a vote also gives a much bigger advantage to establishment candidates (ironically the opposite justification is given for starting the process in small states like Iowa and New Hampshire, where retail politics can overcome fund-raising and mass media buys).

So by my observation, SDs with direct votes for the nominee is bad for the process. They give advantages to establishment candidates, they encourage extending close, hard fought campaigns, risking party unity, and if they ever overturned the "will of the people", it would be described as an undemocratic coup by the leading candidate.

I'm interested in other views on this, especially justifications for SDs and scenarios where people think SDs would improve the party's candidate selection.