In politics, campaign advertising is the use of an advertising campaign through the media to influence political debate, and ultimately, voters. These ads are designed by political consultants and political campaign staff. Many countries restrict the use of broadcast media to broadcast political messaging. In the EU, many countries do not permit paid-for TV or radio advertising for fear that wealthy groups will gain control of airtime making fair play impossible and distort the political debate in the process. In both the United Kingdom and Ireland, paid advertisements are forbidden, though political parties are allowed a small number of party political broadcasts in the run up to election time. The United States has a very free market for broadcast political messaging. Canada  allows paid-for political broadcasts but requires equitable access to the airwaves. Campaigns can include several different media (depending on local law). The time span over which political campaign advertising is possible varies greatly from country to country, with campaigns in the United States lasting a year or more to places like the UK and Ireland where advertising is restricted by law to just a short period of weeks before the election.  Social media has become very important in political messaging, making it possible to message larger groups of constituents with very little physical effort or expense, but the totality of messaging through these channels is often out of the hands of campaign managers.