By Brian Wheeler
BBC News political reporter
The Conservatives have said the general election could be decided by as few as 800,000 voters in marginal constituencies.
The Electoral Commission is trying to boost turnout
Tony Blair has said it could be just a few hundred.
So what happens if you are not fortunate enough to be among that number? Does your vote count for anything at all?
And what if the massive increase in postal voting at this election leads, as some observers fear, to a big increase in electoral fraud?
Concerns about the security and fairness of Britain's voting system have, arguably, never been greater.
But although the Liberal Democrats and most smaller parties remain committed to proportional representation - and Labour's manifesto includes a pledge to "review the voting system" - electoral reform is not exactly at the top of the political agenda.
"We would say there is a point in voting - but I can understand it when people say there isn't," says Alex Folkes of the Electoral Reform Society, which campaigns for proportional representation.
It is hard not to feel a little self-conscious when you are standing next to the mayor of London in your stocking feet
Mr Folkes claims Britain's first-past-the-post electoral system "reduces the number of people who are targeted by parties to about 2% of the voting population".
As a result, the ERS says it could safely declare the result in 425 constituencies in England, Wales and Scotland tomorrow morning.
So what is the point in voting on 5 May if you live in a safe Labour, Conservative or Liberal Democrat seat?
"To express confidence in the system of democracy," says Mr Folkes.
"A lot of other things are also decided on the share of the vote, such as nominations for the House of Lords or whether your party is entitled to party political broadcast, and local elections are also taking place on 5 May.
"These are not huge things, but they are important."
He dismisses suggestions that proportional representation would break the link between MP and constituency - always cited by Tony Blair as the reason for maintaining the status quo - pointing to local council wards, with more than one representative.
The Scottish parliament, which uses a form of proportional representation, proves it can work in the UK, he adds.
Pollsters MORI take a less gloomy view of the general election than the ERS, saying it will be decided by about 20% of voters - no more or less than in previous years.
And MORI's head of political research, Mark Gill, says people tend to vote "because they feel it is their duty" - and are not likely to be put off by lack of confidence in "first past the post".
He also hits back at claims of a bias in the system towards Labour.
Because of population movements that have yet to be reflected in boundary changes, he admits the Conservatives will need to gain 5% more of the popular vote than Labour to gain an overall majority in the House of Commons.
But that figure is a uniform swing across the country - and does not take into account the results in the seats that really matter.
"It is difficult for us pollsters to say what is happening in the marginal constituencies when we do national polls," he says.
Labour, for example, did better in 1997 and 2001 in key marginals than their national share of the vote.
This time the Conservatives are ruthlessly targeting their resources at marginal constituencies and, Mr Gill says, "they are better organised than in 2001. They have more councillors, their morale is clearly higher".
There is also likely to be less anti-Tory tactical voting by Labour and Liberal Democrat supporters, Mr Gill adds.
But what about concerns over vote fraud?
Two vote-rigging scandals involving postal voting in Birmingham and Blackburn have undermined confidence in the system, according to some experts.
"Every time there is a story in the press about vote fraud it reduces confidence in the system," says Alex Folkes.
"People think what is the point of voting when the fraudsters have already decided the outcome.
"I don't think that is the case, but that is how people feel and they won't vote because of it."
The Electoral Commission, which finds itself in the difficult position of criticising the postal vote system, while at the same time attempting to inspire confidence in it, is advising people on its website on how to ensure their ballot is safe.
It says it will be carrying out a review of postal voting after the election, but for many disenchanted voters, that will be too late.