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Can marketing change your vote?

6 March 2015 Last updated at 00:50 GMT

Politics is about selling, especially this close to an election. Politicians have to sell themselves and their products - their policies.

So if they market the policies right and get the right packaging, are people more likely to buy them?

John Humphrys put it to the test in the marginal constituency of Watford, together with advertising expert Gail Parminter.