Limit Presidential Campaigns to 3 months

I would like to see the campaign limited to 3 months.  I believe that the President needs to focus on running the country and not be re-elected.  I believe that there would be less money spent on campaigning this way.  That money could be channeled elsewhere.  I would rather see politicians raise money for charities that they care about and not for their war chests.  I would be more impressed with that.  In this day and age of media and information, I believe 3 months is long enough to get their message out and for us to understand their platforms.