Set the table for bread and butter - or in this case, fruit and veg: Labour fired its opening election campaign salvo on Sunday with a starkly populist pitch for tax-free produce. The party is pushing ahead with the pre-announced policy despite hiccups in the reveal and near-universal opposition from experts - including in its own ranks: a clear sign the party is putting polling ahead of principle.  In this week's Focus on Politics, Deputy Political Editor Craig McCulloch assesses the political calculus behind Labour's vote-grabbing GST policy.