Multiple political parties (Greens, Change UK) believe there is no need for Remain parties to coordinate because the election is held under proportional representation. This is wrong, and misunderstands the role of district magnitude
— Chris Hanretty (@chrishanretty) April 17, 2019
District magnitude = number of representatives elected per district/constituency. The magnitude of the regions used for EP elections ranges from 3 (NE England) to 10 (SE England)
— Chris Hanretty (@chrishanretty) April 17, 2019
The smaller the magnitude, the greater the "effective threshold", or vote share required to get elected in that district
— Chris Hanretty (@chrishanretty) April 17, 2019
A rough rule of thumb: the effective threshold is 75%/(m+1), where m is the district magnitude https://t.co/wPof0jFwYo
— Chris Hanretty (@chrishanretty) April 17, 2019
For a ten-seat region, you probably need 75/(10+1)= 6.8% of the vote to get elected. For a three seat region, it's ~19%
— Chris Hanretty (@chrishanretty) April 17, 2019
You cannot (easily) move from these regional thresholds to national thresholds https://t.co/wPof0jFwYo again pic.twitter.com/RJhinUPYWQ
— Chris Hanretty (@chrishanretty) April 17, 2019
But district magnitude (rather than methods of seat allocation like d'Hondt) are what create incentives for parties to coalesce
— Chris Hanretty (@chrishanretty) April 17, 2019