Circumstances surrounding this vote is completely different then previous ABC ones.
Every time ABC was used it was with Liberals being in clear second. This time it was very different with NDP in second. This time lots of discussion of coalition and liberal/NDP mergers, not just from Harper but mainstream media.
Even if people ignored that, the NDP were getting very close to conservatives in polls and it seemed possible based on some NDP would get minority.
It could make possibility of Layton being in power if you vote ABC simply. Lots of people might hate Harper being in power but they could hate even more NDP.
Ask older people in Ontario, do you hate Mike Harris reign? You'll get a lot of yes. Ask if they hated Bob Rae reign? You'll get even more.