How can they know? Polls? Why not just let the pollster vote for you?

People lie to pollsters to keep thier intents secret. This is why exit polls should not be broadcast during national elections.

some seats are so entrenched it isn't worthwhile bothering to vote the other way. some are swinging seats, and with the others, parties can decide for themselves whether they want to concede...that's CONCEDE...so they may decide not to concede and to fight it. but i think you'll find they will be willing to concede a few.

I still want to vote for the candidate I want in the position. If enough people are apathetic enough not to vote my candidate has a chance to unseat the opposition.

You mistake the reason for voting. It is not to elect the latest corporate pap repeater; but to give the government authority to rule you even though it has none of your interests in mind. Dictators love voting for this reason - so why not have a fake vote every few years where computer servers defraud all statistics to produce a false result - its the design for a legitimised coup.

Alternatively, employ proportional representation across a district five times larger than today's, with five offices up for grabs. That way no one would be disenfranchised.