I'm 27 and this is the first federal election I've voted in where I didn't vote conservative. I even voted for Harper, twice.
Why the change of heart?
Because regardless of your political leanings, it is important to be able to objectively look at the record of the man in power and decide if he has your country's best interests in heart. Out of all the Prime Ministers I have seen over my life, and there have been a few, Harper is the only one who genuinely terrified me of what he would and could do if he remained in power. Anyone who muzzles scientists, destroys our environmental protection efforts, paves the way to undermine the Charter of Rights and Freedoms to spy on Canadian citizens, and leads the country in increasingly undemocratic ways while ruling with fear-based rhetoric that targets Muslims as scapegoats as Jews and other minorities have been in the past by other governments is not a man I trust to lead our country. This isn't even to mention how badly he's tarnished our reputation internationally.
I find it infuriating when people vote for the same party, no matter what, because that's what their family has always done, or what their region has always done. I'm pretty sure Hitler's undisguised clone could run for Prime Minister, and Alberta and Saskatchewan would without fail vote for him, so long as he was Conservative. There's nothing wrong with having political leanings; just make sure you're willing to compromise if the guy running your party of choice is what you want to see in power.
The Americans have a similar choice coming up between Trump and Carson. On one hand, you have a misogynistic asshole whose ex wife said he used to sleep with a copy of Hitler's speeches beside in his every night in an interview in the early 90s, and a man who is trying really hard to appeal to fundamentalist Christians by saying shit like evolution is the work of Satan and that the Great Pyramids were grain silos.
The US scares me because anyone who's in any way moderate or willing to work with the opposition party will never, ever get elected. It's a game of who can be the most polar opposite of the other party, not what's best for the country.