I recommend this article in This Magazine on the NDP campaign during the 2004 federal election. While I don’t endorse all of it there is some interesting and original background worth reading. In particular I would highlight the following two passages:
About the NDP TV ads:
Despite the high-profile TV spots, marketing experts say the message was soft. Early ads touched briefly on issues like health care, cities, pensions and the environment, but didn’t focus on one point in particular. “If they’d given [voters] something to latch on to, they may have done better,” says Richard D. Johnson, chair of the department of marketing, business economics and law at the University of Alberta. Marketing specialist Martin Wales agrees. “They didn’t give me enough reason to vote for them—they didn’t present anything unique.”
This point was also made by TC Norris here. See the section on the NDP.
About the NDP’s failure with respect to strategic voting
“The biggest weakness of the campaign was the inability to figure out what to say to voters about the threat from the right,”(York U. Prof Jim) Laxer says. He points to the NDP’s attempts to dismiss the Liberals as Conservatives in disguise as a huge mistake. In June, the party launched an Ontario-only TV ad that pegged Stephen Harper, Dalton McGuinty and Mike Harris together. “I would regard myself as someone on the left, but when they try to tell me that the Liberals and the Conservatives are the same, what’s left of my hair stands on end because I just don’t buy it.”
The NDP needs a case for why they deserve votes and not the Liberals but as Laxer notes, the argument that the Liberals and the Conservatives are the same is not it. Having said that, the key factor, (to which the This Mag article does not do justice) was the urban fear of a highly conservative social agenda on the part of the Conservatives. This had the effect of driving voters to the safety of the Liberals who are, by and large, socially liberal.
I can't think of what the NDP might have done about this. Circumstances sometimes are against you no matter what you say or do. Such was the case for the NDP in 2004. For their part, the Liberals, having initially planned to go strongly after Conservative voters, recognized that they needed a strategic shift to a more progressive profile to win.