The Halo Effect is the idea that global evaluations about a person (e.g. she is likeable) bleed over into judgements about their specific traits (e.g. she is intelligent). Hollywood stars demonstrate the halo effect perfectly. Because they are often attractive and likeable we naturally assume they are also intelligent, friendly, display good judgement and so on. That is, until we come across (sometimes plentiful) evidence to the contrary.
In the same way politicians use the ‘halo effect’ to their advantage by trying to appear warm and friendly, while saying little of any substance. People tend to believe their policies are good, because the person appears good. It’s that simple