Robust political debate is part of a healthy democracy, but sometimes things can go too far.
The National Police Chiefs Council, working with the Crown Prosecution Service and the Electoral Commission, have produced guidance for candidates and campaigners, to help you understand when behaviour goes beyond political debate and may be unlawful. It also provides more detail as to the nature of possible offences, and some other sources for advice on keeping yourself safe, including online.
If you feel that behaviour towards you may be unlawful or are concerned for your safety or that of others, you should always contact the police.