A small number of West Midlands constituencies could have handed victory to David Cameron's Conservatives if an election was held this week.
According to research by the Electoral Reform Society, voters in seats such as Stourbridge, Edgbaston and Redditch hold the balance of power.
It published findings to coincide with the date Gordon Brown was reportedly planning to hold an election.
Last month there was mounting speculation the Prime Minister was preparing for an election on November 1. But Mr Brown announced there would be no poll this year, and probably not next year.
The society said changes to our voting system were needed to ensure every vote was equally valuable.
It said there were just 67 seats which held the key to a Conservative victory.
They include Stourbridge, Birmingham Edgbaston, Stafford, Burton, Redditch, Wolverhampton South West, Tamworth and Worcester. These are all Labour-held seats the Conservatives hope to gain.
The society named Rugby and Kenilworth as key. This is a marginal seat which the Conservatives took from Labour with a small majority in 2005.
The society claimed most voters will have no say in the contest, because Britain's "first past the post" system means only voters in marginal seats make a difference.
And just 8,000 votes in the right constituencies could be enough to rob Mr Brown of his majority and create a hung Parliament.
Ken Ritchie, chief executive of the Electoral Reform Society said: "Brown's opponents may be claiming a new government needs a mandate. Well a mandate delivered by 8,000 people in the swing seats is no mandate at all."