In a seminar I chaired at the Fabians conference yesterday I asked Peter Kellner of YouGov whether it was possible to judge what was the more effective form of political campaigning: the Conservatives spending millions on billboards of an airbrushed David Cameron, or Labour supporters parodying it with the www.mydavidcameron.com pics, which have now received considerable coverage in the mainstream media. His response was that it's difficult to judge, and that 90% of the money spent by the political parties during election campaigns is a complete waste of money anyway. Leaflets go in the bin, billboards are forgotten, etc, etc.
Also, much of this propaganda is directed at people who have already made up their minds how to vote anyway.... Which is why Voter ID/ phone bank work, and then targeted mailings are by far the best use of funds rather than blanket coverage of a constituency. (Not something those with the Ashcroft millions behind them have to worry about though - they can just bombard everyone.)
The received wisdom about billboard campaigns in the past was that what mattered wasn't the billboard itself, but the press/TV coverage it got when it was unveiled. As Peter Kellner pointed out, the only Conservative billboard people remember from the 1997 campaign was the 'Demon Eyes' picture of Tony Blair. And yet there was only ever the one poster; it wasn't a campaign that was rolled out on billboards across the country. You will probably be able to find people who can "remember" seeing the poster, but they won't have; they'll have seen the press coverage.
During my brief stint working for the Labour Party during the 2001 election I remember having trouble explaining this to the Electoral Commission, when we were discussing election spend with them. They were convinced that a 'billboard campaign' would have cost millions, whereas the truth is, most of them only get a very limited run. The current Cameron campaign, which really has been rolled out nationwide, is the exception, not the rule. And yes, people notice the posters, but are they more or less likely to vote Conservative as a result? I doubt it actually makes any difference at all, unless the ad agencies find a campaign that really hits home.
At the coming election Labour has a choice - should it spend its limited funds on targeted mailings, phone banks, battle buses, party political broadcasts, new media campaigns: all those things which genuinely connect with voters? Or should it splash out on billboards instead? My reckoning is we might see one or two limited poster campaigns, to get across a particular message on a particular day, perhaps in a particular location, but we won't be following the Conservative example.