Much is always made about polls and who the polling companies are "biased" toward. A recent poll shows approval of Harper and the Tories waning BEFORE the Julie Couillard/Maxime Bernier affair. Some have questioned the intermittent timings of polls by this company, when they seemed to be polling a lot more when the Cons were riding high. There are also the usual barbs about this firm leaning towards the Cons or the Libs.
Most polling firms have done work for both parties - while IN AND OUT of government. This is a key point. Polling companies and "consulting firms" can gain a lot from lucrative government contracts. One clear observation is that they tend to "nurse" the party in power up to the point it seems that they shouldn't - due to genuine voter angst or mistrust. When the party is "going down" they quickly start finding friends in the soon to be government. You often see former advisers and "hangers-on" of governments seeing themselves potentially losing their Hill jobs, then opening political polling/consulting firms to try to appear "unaffiliated" or "neutral". Working on the Hill for a while generally nets you a few friends on the "other side" (most partisan voters would be shocked at how many friendships there are between party staff on the Hill - although the Cons seem to be a bit further removed - you need to show some real ideological leanings before you can be their friend).
Polling firms tend to favor the results they want to see: When you hear "a whopping 42% of Canadians do not disapprove of the government", what do you think? If you confuse that with the 40%-plus needed to be in "majority" territory - or if the pollster makes the distinction "hazy" for you, you may be led to believe the government is ready for a majority. The same number, however, also implies that 58% of voters DISAPPROVE of the government. Taking a closer look at the 42%, you may also find that 32% may ACTUALLY approve, while 10% may simply think that they "haven't enough evidence to disapprove", or are "undecided". If you break it along partisan lines, someone could interpret the numbers to mean that the government is in majority territory, but that the opposition is split with numbers in the 20s, or lower.
Bottom line is that you can play with numbers, or a biased media (who usually pay for these polls) can choose to headline what they want from a poll, cherry-picking what suits their needs at the time. It's best to take polls with a grain of salt. The Julie Couillard/Mad Max scandal is currently being polled... We will see if the various media, pollsters, "consultants", etc., start opening up their allegiances a little bit to include a little more disapproval of the ineptness of the Harper government...