I agree that most voters decide who to vote for based on their own values and, biases and therefore they are not easily swayed by campaigns. However, harking back a long way to the sixties we should not ignore the effect of the media when JFK beat Nixon. The media focusses largely on personalities not policies, whilst most voters are concerned with day to day effects of policies on their lives.
Closing down an election campaign would entail all media including social media. It would be desirable but it's naive to think it possible.
I am very interested in those constituences that contradict their MP as already referred to. This is not going to be an "ordinary" election and I can't see the outcome as anything other than a hung parli ament.
Sadly I can't see any politician in my constituency that I have the regard for to deserve my vote.