The real story of this election was a lack of a progressive pact/tactical voting killed the progressive parties, and that MUST be addressed in 2024 to kick the tories out. If you combine the CON/BRX/UKIP vote and pit it against the LIB/LAB/GRN/Prog independent vote, these 44 seats would have flipped (margin in parenthesis). Note that I'm only looking at English seats in this post.
1. Wimbledon (23.2)
2. Kensington (21.3)
3. Cities of London and Westminster (19.7)
4. Finchley and Golders Green (12.4)
5. Chipping Barnet (10.6)
6. Carshalton and Wallington (10.5)
7. Guildford (10.2)
8. Watford (9.0 )
9. Cheadle (8.1)
10. Truro and Falmouth (8.0 )
11. South Cambridgeshire (7.4)
12. Wycombe (6.3)
13. Hitchin and Harpenden (5.3)
14. Southport (4.
15. Lewes (4.0 )
16. High Peak (3.
17. Warrington South (3.6)
18. Chingford and Woodford Green (3.4)
19. Cheltenham (3.2)
20. Reading West (3.2)
21. Winchester (2.9)
22. Altrincham and Sale West (2.7)
23. Bury North (2.4)
24. Hazel Grove (2.4)
25. Hendon (2.4)
26. Rushcliffe (2.3)
27. Bury South (2.2)
28. Gedling (1.
29. Wolverhampton South West (1.6)
30. Filton and Bradley Stoke (1.2)
31. St Ives (1.1)
32. Woking (1.1)
33. Milton Keynes North (1.0 )
34. Pudsey (0.
35. South West Hertfordshire (0.
36. Wokingham (0.
37. Bolton North East (0.6)
38. Chelsea and Fulham (0.6)
39. Dewsbury (0.2)
40. Sutton and Cheam (0.1)
41. Esher and Walton (0.1)
42. Stroud (0.1)
43. York Outer (0.1)
44. Derby North (0.1)
Notice how most of these seats are in the South, particularly Metropolitan London. Sure, a few of the Labour heartland seats could have been saved with a progressive coalition, but on the whole, the easiest seats to win are in the South. Furthermore, trends towards the progressive parties in the South have been particularly dramatic, with many constituencies in Oxfordshire, Buckinghamshire, Hertfordshire, and Surrey swinging 20+ points towards the progressives since 2015. This is where the election will be won in 2024, and that's part of why I think someone like Sadiq Khan should lead Labour going forward. Applying 2015-19 trends again coupled with a full progressive party pact, in 2024, these flips occur basically no matter what:
1. Kensington
2. Cities of London and Westminster
3. Wimbledon
4. Guildford
5. Hitchin and Harpenden
6. Chipping Barnet
7. Esher and Walton
8. South Cambridgeshire
9. Woking
10. South West Hertfordshire
11. Finchley and Golders Green
12. Wokingham
13. Chelsea and Fulham
14. Watford
15. Truro and Falmouth
16. Winchester
17. Chingford and Woodford Green
18. Altrincham and Sale West
19. Rushcliffe
20. Bury South
21. Reading West
22. Filton and Bradley Stoke
23. Cheadle
24. Bolton North East
25. East Worthing and Shoreham
26. Wycombe
27. Carshalton and Wallington
28. Wantage
29. Bournemouth East
30. Milton Keynes North
31. High Peak
32. York Outer
33. North East Somerset
34. South West Surrey
35. Milton Keynes South
36. South East Cambridgeshire
37. Cheltenham
38. North Somerset
39. Morecambe and Lunesdale
40. Aylesbury
41. Beckenham
42. Hastings and Rye
43. Warrington South
44. Bromley and Chislehurst
45. Epsom and Ewell
46. Mid Sussex
47. Hazel Grove
48. Beaconsfield
49. Pudsey
50. Northampton South
51. Uxbridge and South Ruislip
52. Totnes
53. Bury North
54. Loughborough
55. Croydon South
56. Bournemouth West
57. Chesham and Amersham
All of these seats flip with a progressive coalition and trends, even if the Conservative coalition wins the popular vote by 5+ points. Again, the vast majority are in the South, and the North remains mostly out of reach. Of course, they'll be offset by a few inevitable flips in Wales and Northern England (perhaps the Welsh Valleys will finally go), but in these places, Labour is mostly constrained to the big cities and has far fewer vulnerable seats than these ones. Besides, after that, there are still more competitive seats:
58. East Devon (flips if Conservatives win national vote by 5 points)
59. Welwyn Hatfield
60. Keighley
61. Macclesfield (flips if Conservatives win national vote by 4 points)
62. Shipley
63. Reigate
64. Wolverhampton South West
65. Crawley
66. Banbury
67. Henley
68. Worcester
69. Stroud
70. Tunbridge Wells (flips if Conservatives win national vote by 3 points)
71. Harrogate and Knaresborough
72. Romsey and Southampton North
73. Witney
74. Runnymede and Weybridge
75. Mole Valley
76. Lewes (flips if Conservatives win national vote by 2 points)
71. Southport
70. Gedling
71. Lincoln
72. Maidenhead
73. St Ives
74. Sutton and Cheam
75. Norwich North
76. South Swindon (flips if Conservatives win national vote by 1 point)
77. Huntingdon
78. South Thanet
79. Peterborough
80. Worthing West
81. Dewsbury
82. Ruislip, Northwood and Pinner
83. Derby North
84. Shrewsbury and Atcham (flips if national vote is tied)
85. Harborough
86. Bastingstoke
87. Arundel and South Downs
88. Colne Valley
89. Southampton Itchen (flips if Progressives win national vote by 1 point)
90. Hexham
91. Newbury
92. Birmingham Northfield
93. Stevenage
94. Central Devon
95. Calder Valley
96. North East Hertfordshire (flips if Progressives win national vote by 2 points)
97. Chichester
98. Northampton North
99. Telford
100. West Bromwich East
101. Hemel Hempstead (flips if Progressives win national vote by 3 points)
102. Torridge and West Devon
103. West Dorset
104. Rochester and Strood
105. Hendon
106. Heywood and Middleton
107. Chelmsford
108. Hertford and Stortford (flips if Progressives win national vote by 4 points)
105. Salisbury
106. Ipswich
107. Gloucester
108. Somerton and Frome
109. Isle of Wight
110. Windsor
111. Pendle (flips if Progressives win national vote by 5 points)
Obviously, these figures are a bit crude, but there are two clear takeaways: there needs to be a progressive coalition and 2024 will be won in the traditionally Conservative South. What this means now, is that the Greens, Lib Dems, and Labour need to reach some consensus on a unifying, center-left message which is pro-immigrant, pro-Europe, pro-environment, pro-working and middle class but not anti-business; and consistently hammer the Conservatives on the same talking points. Regardless, trying to win back the small-town postindustrial North isn't going to work.