Cambridgeshire is a good example of how difficult it is to predict the outcome of this general election.
Cambridgeshire has a rapidly growing population, lots of 2024 voters will not have been in Cambridgeshire in 2019. As a result Cambridgeshire gained a seat in the recent boundary review, going up from 7 to 8. St Neots and Mid Cambridgeshire is the new constituency, but there are significant boundary changes to most of the other constituencies.
In 2019 the Conservatives took all of the seats except Cambridge, which was Labour.
Cambridge and North East Cambridgeshire are the only two constituencies where the outcome can be predicted with real confidence, with Labour holding Cambridge and Conservative holding North East Cambridgeshire. The most interesting feature in Cambridge will be whether the Greens can take second place ahead of the LibDems, who will be concentrating their campaign resources elsewhere (see below).
Two seats very likely to change hands are Labour winning Peterborough and LibDem winning South Cambridgeshire. Both of these only need relatively small swings but, on the other hand, a lot of tactical voting is possibly already "baked in".
The other 4 constituencies are very difficult to predict, the outcomes will depend on influx of new voters, size of swing, and extent of tactical voting. All of them start from a point where the Conservatives probably won in 2019 with more than 50% of the vote on the new boundaries, so, in the past, tactical voting has not been a significant factor.
In St Neots and Mid Cambridgeshire, and Ely and East Cambridgeshire, the LibDems probably start the campaign best placed to challenge the Conservatives, but with about 20 percentage point gaps to close. The St Neots and Mid Cambridgeshire new constituency is especially difficult to predict because it includes the rapidly expanding new towns of Cambourne and Northstowe, and is also the constituency most affected by East West Rail. The extent of tactical voting for the LibDems could be key here.
In North West Cambridgeshire (which includes most of Peterborough south of the River Nene) and Huntingdon (which also includes St Ives), Labour probably start the campaign best placed to challenge the Conservatives, but with even bigger gaps to close than the LibDems have in St Neots and Mid Cambridgeshire or Ely and East Cambridgeshire. Labour will only be able to take these in a landslide victory. To demonstrate the scale of what we are talking about here, Huntingdon was John Major's constituency.