Could tactical voting determine the outcome of the election? Which parties would benefit and who might lose out? And why is Carol Vorderman getting involved? Political editor Paul Francis crunches the numbers…

Most people vote for a candidate in an election because they are closest to their policy proposals. But others put a cross against one because it might prevent another party from benefiting.

It’s the phenomenon known as tactical voting and interest in it has grown over the years, reflecting the frustration many voters have about their voices counting for nothing under the the first-past-the-post election system

Those who back it often do so for different reasons and changes in the political landscape of Kent have led to less certainty about its potential impact.

Two key elections in the county demonstrate how it is said to have been instrumental in the eventual outcome. In 2017, Labour won Canterbury against expectations, ending a mostly uninterrupted period of Conservative control stretching back to 1835 - a feat that earned it a place in the Guinness Book of Records.

A typical three-way constituency, the Conservatives had previously benefited from the split vote between Labour and the Liberal Democrats,

In 2017, the unexpected outcome was partly attributed to students who it was said had two potential votes if they were on electoral registers both at home and in Canterbury.

Evidence either way was hard to come by but it was possibly a case of the Lib Dems ‘lending votes’ to Labour.

Two years earlier and tactical voting also played a part in the general election in 2015, where the then Ukip leader Nigel Farage stood in South Thanet and failed in what was his seventh bid to become an MP - thought largely to be attributable to a coalition of support for the Conservative candidate Craig Mackinlay.

Perhaps the most blatant example of tactical voting in Kent came in 2019 - again in Canterbury - a marginal seat heavily targeted by the Conservatives. With weeks to go, the Lib Dem candidate Tim Walker announced he was not going to stand and urged party supporters to swing behind Labour’s Rosie Duffield. He said he did not want to split the support for remaining in the EU.

But he failed to persuade party chiefs to consider not fielding a candidate at all, although they might as well have done as the replacement trailed in a lowly third place.

Fast forward to 2024 and there are mixed views on the impact of tactical voting. The Liberal Democrats in Tunbridge Wells are actively encouraging voters to consider the option, saying that disaffection within Tory ranks enhances the possibility of an upset in the constituency, now an official target.

The problem for the Lib Dems’ candidate Mike Martin? Labour is not playing ball. Its candidate Hugo Pound unambiguously says he does not support the idea.

Campaigners for changes to the voting system argue that under the current arrangements, millions of votes count for nothing.

Why? According to the Electoral Reform Society, votes cast for non-elected candidates, or for winning candidates which are over and above what they need to be elected, are thrown on the electoral scrapheap.

It studied the 2019 results and concluded “a staggering number of voters saw their vote count for nothing”.

Across the UK, 14.5 million people’s votes were ‘surplus’. In other words, they were cast for the elected candidate but did not contribute to their election. All in all, more than 22.6 million votes (70.8%) did not contribute to electing an MP.

However, there is support from the campaign group Compass, which backs electoral reform and a switch to some form of proportional representation. The Kent branch is urging voters to back the Mr Martin in Tunbridge Wells.

It is also backing Helen Whitehead, Labour candidate for Herne Bay & Sandwich, who is trying to unseat veteran Tory Sir Roger Gale.

Compass says its backing for the two follows close analysis of the constituencies, which shows that both candidates are best placed to win with the help of a tactical voting campaign.

Compass says its support is contingent on the two candidates supporting wholesale reform of democracy - starting with replacing first-past-the-post with proportional representation..

Mr Martin said: “Having a fairer voting system would mean that everyone’s vote counts.

“In so many ‘safe’ constituencies, everyone’s vote is wasted because we know who is going to win.

“That’s not right. Every voter should be and feel heard.”

Ms Whitehead said: “I do not believe that we can say without doubt that there is any one system that can conclusively deliver healthy democracy without challenges; but I know that the conversations to enable change are essential.“

But Hugo Pound, Labour’s candidate in Tunbridge Wells, said: I don’t support tactical voting.

“You lose out either way; you either get someone who does not represent your true values or they fail to win and you’ve wasted your vote.”

The issue has spawned many websites which offer advice on who to vote for in order to enhance the chances of preventing the Conservative candidate from retaining or securing the seat.

Among the more influential is one that Carol Vorderman, the TV presenter, is heading called “StopTheTories.”

She claims that half a million people have used the site to get advice on who to back and says tactical voting offers “the chance of a lifetime” to push the Conservatives out of power for a generation.

Tactical voting is not a new political phenomenon but those who back it often do so for different reasons and changes in the political landscape of Kent have led to less certainty about its potential impact.

The case that the Conservatives have an unfair grip is persuasive on one level.

Although the Lib Dems were not without problems back in 2019, 11.5% of people voted for the party, but they only secured 1.7% of seats.

The Conservatives’ 43.6%, on the other hand, translated to 56.2% of seats.

It is why campaigners who believe that the system is skewed towards some parties frequently point out that the MPs elected to Parliament rarely reflect the popular vote.

In Kent, the issue of tactical voting has had some support historically but not on the scale required to break the cast of first-past-the-post.

Advocates for reform tend to gravitate towards classic three-way marginals when they are making the case for change. In Kent, that has meant seats like Folkestone and Hythe, Canterbury and, more recently, Tunbridge Wells have come under the spotlight.

The new leader of Maidstone Borough Council, the Green party’s Stuart Jeffrey says the appetite for pacts and tactical voting is not as great as it was, partly because the Conservatives are not the political force they used to be when it was virtually impossible to dislodge them.

He claimed: “Labour are going to win the election and the Conservatives are going to lose… what that means is that you can vote with your conscience.”