STV and multi-member districts are accused of producing intra-party friction but contests are not zero-sum

The multi-seat constituencies required by STV mean that candidates must often compete for election with others from the same party. 

But multiple candidates of the same party are elected in cases where that party has enough votes, so it is not zero sum.

There may be competition but both (or neither) may win.

As well, intra-party friction is reduced by the fact that under STV, candidates that are akin to each other try to get the other's supporters to mark themselves as their secondary preferences.

if you act meanly toward the other candidate, his or her supporters are not likely to mark you as a back-up preference. 

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