The Liberals need to respond, any commentary presmes a sense that lessons have been learned, a measure of adaptability, given previous experience. Apart from that assumption, looking only at the Conservative tactics, it's not a strong presentation. The Conservatives themselves "held back", because even within their partisan brains, they understood the inherent negatives in attack ads, at this time. There was a sense of reinforcing unpleasant narratives, relating to Canadians view of Harper and how he conducted himself. There was the danger of going negative during an economic downturn, which allowed for easy counters as to government priorities. We assume the PMO understood the following retort was a given:
Trust the Conservatives to get attack ads out faster than they can deliver their promised stimulus funding. Unable to provide leadership himself, Stephen Harper has launched new ads attempting to divert attention away from his government's failures to fix the economy and to undermine the credibility of the one leader he knows can take his place
Calculating a real opportunity for blow back, the Conservatives held their fire. Those dynamics haven't changed, all that's happened is a tipping point in thought process, borne of "desperate times". If you're scanning the various news items and opinion on this story, almost without exception the ads are discussed within the context of falling Conservative fortunes, a sense that Ignatieff is resonating and the Liberals on the move. That translates to this release coming from a perceived position of weakness, rather than the Big Blue Machine laying waste to their opponent. Nobody frames these ads as an example of the former "strategic brilliance", but more rightly, as a sign that the Conservatives are LOSING. The fact that the previous thinking has been abandoned, these ads released, provides official confirmation that within Conservative circles, they also believe they are LOSING.
I don't find it necessary to rationalize the dangers of these ads for the government from a Liberal perspective, because you find objective truth within Conservative circles, and those previous hesitations underscore simple facts. If, we are in situation wherein that previously sound logic has been replaced because poor circumstances demand it, then it tends to blunt the true impacts. The Conservatives are desperate, and they know it. That's the backdrop here, and that clear fact admits a relatively good position for the Liberals. These ads have a "hail mary" element, which by their nature speaks to real, concerning weakness, so one can modestly grin at the wishful bombast coming from the minions. This is fear, not formidable, which makes the entire proposition a dicey affair.