I rather suspect that the reason for “oppose” votes comes from the voting formula:

http://meta.wikimedia.org/wiki/Wikimedia_Foundation_elections_2015/Vote_Questions#How_are_the_winners_determined.2C_and_what_is_the_process_once_voting_is_completed.3F

which declares the winners to be those with the highest

Support/(Support+Oppose)

As they say, “do the maths” (or if you are American, “do the math”).

If you are just voting to support anyone who you feel would do a reasonable job, you have no real motivation to cast “oppose” votes. But if you are particularly seeking the election of a particular candidate, then you increase their chances by casting oppose votes for the others.

Just as a simple example. If there are 2 candidates, Andy and Betty. Let’s suppose 10 people think Andy would be a good choice and give support votes for Andy. Let’s suppose 10 other people think Betty is a good choice and give support votes for Betty.

Andy’s score = 10 * (10+0) = 1

Betty’s score = 10 * (10+0) = 1

Both are equal.

If just one of Andy’s supporters gives an oppose vote to Betty, what’s the situation?

Andy’s score = 10*(10+0)= 1

Betty’s score = 10*(10+1)= 0.909090

Winner: Andy.

It’s strategic to “oppose” other candidates. It’s not necessarily saying anything against the opposed candidate personally.

Kerry