The UK is set for a general election on 12 December, as the country tries to find a way past the current Brexit impasse.
This election is very different from those that came before - because for many voters, it will be something of a second referendum on Brexit.
What happens with Brexit after the election could depend on how many pro-Remain MPs, or pro-Leave MPs win seats.
The Conservatives are campaigning on Prime Minister Boris Johnson’s new Brexit deal, agreed with the European Union.
The Labour party has promised a second referendum within 100 days of the election, should it take power, and other opposition parties such as the Liberal Democrats and Scottish National Party want to stop Brexit altogether.
Therefore tactical voting could play a crucial role in this election, more than any other in recent history.
What is tactical voting?
In UK general elections voters in a constituency choose their MP, and the party that achieves a majority of MPs in Parliament wins.
Tactical voting takes place because — under the UK's first-past-the-post system — some seats are only realistically contested by two or three different parties.
Therefore if a voter’s desired party doesn’t have a chance in that seat, they may instead vote for a different party; one that aligns somewhat with their beliefs, or one that has the best chance of keeping some other party out.
Splitting the vote is also a huge consideration. In this election, for example, Leave voters would want to avoid the risk of splitting the vote between two Leave parties in the same seat, such as the Conservatives and the Brexit Party, and therefore handing victory to a Remain candidate.
How would it work?
One organisation that wants to get voters voting tactically to win a pro-Remain majority in Parliament is Best for Britain, which claims it is a “cross-party campaign with a mission to stop Brexit by any democratic means”.
It has set out what it believes is a roadmap to Remain victory, with a tool on its website inviting users to enter their postcode to find out who they should vote for to get the best chance of a Remain-supporting MP in that seat.
The campaign predicts that if 30% of pro-Remain voters vote tactically it would prevent the Conservatives from getting a majority, and with 40% voting tactically a coalition of Labour, Liberal Democrats, SNP, Green and Plaid Cymru would hold a majority of 36 seats in Parliament.
A number of other pro-Remain tactical voting apps and website have also been launched.
Pro-Brexit campaign group Leave.EU has promised voters an app that will do the same on the Leave side, recommending a single pro-Brexit candidate in each constituency who will have the best chance of winning the seat.
One example of a marginal seat where tactical voting could make all the difference is in the Richmond Park constituency in London. At the last election in 2017, the Conservative candidate beat the Liberal Democrat by just 45 votes. The Labour candidate came a distant third but still took more than 5,700 votes.
Whether tactical voting will work in this election will remain to be seen, but a recent poll found nearly a quarter of voters were ready to vote tactically.