The SNP have gone for the really negative boot in their fight against Labour in Scotland. This fits neatly with their slogan: 'It's Time'. The problem is that negative advertising may well be remembered and act as a mental cue to voters; but it can also turn off voters as easily. A major US study maintained that negativity created poor perceptions of the attacked as well as the attacker. The only ads that are argued to have a positive impact are TV-based and comparative, so allowing the voter to make their own mind up guided by the persuasive narrative. It is suggested that this blunt style may not work, despite doubtless having some resonance north of the border.
The interesting part is the lack of any party branding apart from that of Labour, this brings a new facet to negativity. You can sponsor an ad and publish it but you can obscure the messenger and just rubbish the opposition. Hence this offers win-win potential, particularly in its viral email form. Progress perhaps, though whether it should be lauded is questionable.