Polls show a lot of volatility

A new poll has come out from Harris-Decima that completely contradicts the Ipsos poll of a few days ago:

The Conservatives and Liberals appear to be ending the year the same way they started it — in a dead heat.

A new poll by The Canadian Press Harris-Decima suggests the Tories have the support of 31 per cent of Canadians, statistically tied with the Liberals at 29 per cent.

The poll puts the NDP at 15% and the Greens at 11%, both noticeably higher than the Ipsos results. The Ipsos poll was conducted between the 7th and 9th; the Harris-Decima one was conducted between the 2nd and the 13th. So it's pretty clear that at least one of them must be wrong. Which one? On the one hand, the Harris-Decima poll has a larger sample size (2,022 respondents vs. 1000 for the Ipsos poll); on the other hand, the Ipsos poll, having been conducted in a shorter time period, might provide a better snapshot (and 1000 is still not an unreasonable size). The moral? Nothing really, except that it's hard to predict how the actual election will play out.