At the campaign's final weekend, it appeared that the three major political parties in Great Britain were in a near tie, with the Conservatives or Tories (led by David Cameron) drawing a little more than 30% in the most recent polls, while Labour (led by Prime Minister Gordon Brown) and the Liberal Democrats (led by Nick Clegg) were both slightly below 30%. This could produce a "hung" parliament with no overall majority in the House of Commons, leading to deadlock, new elections, a more-or-less-formal coalition or an inter-party understanding. such as those between Labour and the Liberals in the 1970's.
The lack of a single-party majority would also increase the bargaining power or influence of any independents or minor parties who win representation on May 6th, such as the Scottish nationalists, the Welsh nationalists and the Northern Irish parties.
While there's been no formal coalition government in the United Kingdom since 1945, various forms of wartime or peacetime coalition, such as the National Government, were the norm from 1914 to 1945, interrupted only by single-party Tory governments in 1922-23 and 1924-29.