From its inception the Reform/Alliance/New Conservative Party has been screaming about "fixed election dates". It is an idea that had pervaded the reform ideology, and any time you engaged a Connie you received a litany of their usual tripe - with the fixed dates being one of their top promises.
The promise goes back beyond Harper. And let's not even call it a promise... it was a demand. Rank and file Reformers spewed this stuff out on Prairie doorsteps from the late 80s - right up to - oh... let's say a few weeks ago? I can still remember both Preston Manning and Stockwell Day screaming about the need for fixed dates.
Is this a major promise broken by Harper? As far as promises go, I would say that all PMs have broke a few. The last governing Liberal Party did set a record by keeping between 70 and 80% of their Red Book promises... This record number of promises kept was never matched by another government. We're talking about multi-paged documents containing 100s of liberal ideas. This number was so hard to match that Harper and his Reform-a-tories knew they had to scale down the promises... hence his "5 pillars". Getting back to whether this was a promise, I would say it is more of a "law" that Harper has broken... Promises that are voted on in Parliament and made into those pesky things called "rules" are usually termed "laws"...
Life's pretty easy when you only have to own up to 5 promises... Forget the fact that you promised millions of seniors not to tax income trusts... and hmmm... weren't there a few other promises there? Sure there were. Still, Harper's Republican strategists had it fairly well-planned out when they decided to narrow down the promises so much. Better odds.
The lesser promises made by the Conservatives probably had one other important reason for being, (or "not" being): The Conservatives are a party devoid of ideas. Being a "small tent", "one wing of the political spectrum" party, they are pretty much a "two or three issue party". They couldn't come up with more than 5 ideas (and some they stole from the Liberals - cutting programs then renaming them) because they are more about taking Ottawa apart, and not about building on the legacies and traditions of our great system.
Conservatives are about destroying the institutions which make up one of the most moderate and successful democracies in the modern world. Canada is a great political and cultural experiment, which has existed (after the initial atrocities committed by the European invaders) pretty much in harmony - pretty much without riots, fire-bombings, or civil wars for over 100 years.
Conservatives don't need ideas to build a nation, because they are NOT "nation builders". That role has always been a Liberal one (after the times of MacDonald's "Liberal Conservatives"). Nation building, first of all, requires that you LIKE your nation. You don't call it a "Northern European Welfare State". You don't go to your neighbor's capital and act like you hate it. Nation-builders love their land, and want to keep it the best place on earth. Nation-builders don't let record surpluses and solid infrastructure growth (called an economic miracle in some quarters) turn into the slowest growth in the G7.
You don't need to make promises, if you don't intend to build a nation... Mr. Harper - we know your game... Times up.