The analyst who swung Canada’s elections for Trudeau believes tactical voting could hurt Theresa May

The most useful guide on the web for tactical voting in your area is the Tactical2017.com web site. Open Britain, a pro-Remain tactical alliance, has created this tactical voting guide for people who want to maximise the anti-Brexit vote. There are dozens of marginal constituencies where, if you vote for the “wrong” party, you are essentially helping the Conservatives.

LONDON – The man who helped swing the elections in Canada that propelled Justin Trudeau to power thinks tactical voting could affect the outcome of the UK general election on June 8. There is just one catch – everyone has to know exactly the right way to vote, to maximise their impact. Otherwise, the power of tactical voting is diluted.

“Progressives will strategically vote thinking that a certain candidate might win,” voting analyst Hisham Abdel-Rahman told the Financial Times. Abdel-Rahman’s website pooled votes in the 2015 Canadian elections to favour the Liberal Party. “Without a big plan, everybody’s strategic voting is cancelling out everybody else’s strategic voting.” He told the FT he believes tactical voting could overturn the odds in the Conservatives’ favour (a claim most observers greet with scepticism).

Nonetheless, some Labour supporters and three of its MPs have called for the party to not stand candidates in two constituencies where the Green Party has a better chance of winning in order to reduce the size of the victory that Prime Minister Theresa May is expected to win in the June 8 general election. Labour has rejected the proposal. The party has even expelled some longtime party members who tried to back a pro-NHS independent candidate who has a chance of ousting Conservative MP Jeremy Hunt in a constituency Labour cannot win.

The Green Party has offered a “progressive” tactical alliance with the other parties in order to maximise the anti-Tory vote and keep May’s expected majority to a minimum. Labour turned down that offer. And there is also the pro-Remain tactical alliance, as urged by Open Britain, which has this tactical voting guide for people who want to maximise the anti-Brexit vote. (It has a list of candidates and constituency voting records to help you.)

Underneath the tide – currently flowing in the Conservatives’ direction – there are some interesting cross-currents. The Tories seem to be stealing votes from Labour, which is unusual. The UKIP threat appears to have been neutralised by May. Other than the Tories, only the Green Party and Plaid Cymru gained seats in the May local elections.

In dozens of marginal constituencies – such as Twickenham, Richmond Park, Bath and Berwick Upon Tweed – Lib Dem candidates have the best chance of defeating a Tory candidate. A vote for Labour might actually help the Conservatives in those areas. Similarly, there’s Brighton, currently held by Green MP Caroline Lucas, and the Isle of Wight, where the Green Party is best-placed to defeat the government. Those are two more cases where voting Labour is, in effect, a vote for the government.

But the most useful tool on the web so far is the Tactical2017.com web site.

All you do is find your constituency, and it tells who you need to vote for in order to minimise the number of seats the Conservatives are likely to win, and why. It looks like this:

Now tell us your opinion in our online poll. Are you going to vote tactically in 2017?