Forgive if this turns into a double post, but a post with six quotes + their responses looks too ugly
A few posts up you indicated agreement with Snowman (welcome back, BTW!) that if say, the Green party rose to prominence we'd end up back where we are today, with respect to organizational corruption, etc. that plagues the current system. In both cases, the system itself remains intact. The downside is as Gotchaye described: likely ceding majorities to your opponents, and all the damage (from your point of view) they would do while the third party tried to gather momentum over the course of many elections.
Back in 2000, Nader was blamed (rightly or wrongly) for helping to tip the election to Bush, and look at the fallout over the years that followed for the nation and the world. Your approach would ensure many, many years of that, rather than building a movement to engage in the primary system and make more incremental progress. And I'm not sure it would actually work: there was a backlash against Nader and third parties for (possibly) helping Gore lose, which helped keep them a fringe party in subsequent election cycles. So I'm not even sure that voters would (or should) rally around a third part. Or should, given the potential consequences and the way it conflicts with their desired outcomes.
Regarding Nader, that was an explanation of reality, in the minds of the public, that came after the fact. It made things more difficult for a cleaner Gore win, but...Florida. Had Bush lost, the Green Party would very likely not be as ignored as it is, though third party it would remain.
Most everyone here is agreeing there's at least an institutional problem. My problem with the Democratic strategy, the mainstream strategy, is that it's ultimately susceptible to the same failings and hurdles of any Third Party, with the exception of already existing political capital. Fraud, scandal, and as we've seen with the Tea Party: a mobilized opposition. I have to vote for Democrats hoping that the Republicans are shit enough to scare away moderates and incompetent enough to not get their word out to would-be Republicans. I have to hope that the Republicans do not gain so much momentum with the power of FUD that the Democrats move to the center.
Your example here is a parliamentary system with no executive -- thus heavily proportional -- in which the more leftist liberal party stole seats from the more centrist liberal party, causing the conservative government to get a majority and rule unchecked? And you consider this a victory for liberalism? God save us from such victories.
I don't think anybody is ignoring that. But calling an enormous socialized health care program, gay marriage, support for marijuana decriminalization, economic stimulus, and the DREAM Act "scraps" is a little frighteningly privileged. Believe it or not, I prefer civil rights that are likely to come up in my everyday life to the abstract concerns that the government might be reading my email. Not that it's not something I'd like to do something about, but priorities matter.
first part--based off of what eBay Huckster was talking about, a lot lead up to that. This was the 2011 election, prior to that was Harper's first election as prime minister (2008?) which featured record low voter turnouts. The decline of the Liberal Party had been well underway years prior. I don't see, if the Liberal party becomes decidedly centrist in order to attract more voters, why left voters shouldn't actually coalesce around the NDP. Perhaps by now the stigma of the Liberal brand is dead, perhaps there'd be no rallying point for new voters prior to the NDP surge.
second part--yes, but this also obscures some of the significance of those achievements. Gay marriage/spousal benefit is not a right enjoyed with freedom across the nation, it was a DOMA repeal. Our health care should've been a lot better, and still yet those who need it most, may not see the benefits. Marijuana will take at least a decade to be enjoyed with impunity. Economic stimulus could have been stronger. Things impossible with Romney sure, but also owing to the victories of Right stubbornness. Consider also what we've lost-- gun control, immigration reform, redistricting, the sequester's effects. I understand that you realize that we're dealing with BS, and guessing that you might express support for similar policies as Bo might I don't actually believe that you think the complaints in question are privileged (more so that the rhetoric in making that complaint obscured what has been accomplished), but complaints of the progress we do make are legitimate. At the very least, it's direction for what has to come next.
I fully admit that it might not work, I'll volunteer further that I'm probably biased toward action that causes damage now and not later, assuming that the preferable outcome (people unwedded to the system catapulted into it, pushing reform through before it had their way with them) would even be within reach. All I know with certainty is that I've lost all faith in old blood and institutions. The new, if nothing else, hasn't found somebody to sell its soul to yet.
I'm actually quite similar to you in this post. I make a point to vote, and it's always the left-ing-est Democrats I can shuffle in on the state and national level. I did in fact vote Green in the Presidential election, though i don't consider myself to be a Green. The state I'm in is decidedly Democrat. the process, and a large segment of the voting base, make achieving the desired ends highly tiresome.