For our international posters, it’s worth mentioning that voter ID is being rolled out across England for the first time this election. A non-negligible share of voters don’t appear to know this and/or will not bring an eligible form of ID to the polling station, so expect a bit of a car crash on election day followed by harsh criticism afterwards from some quarters. The partisan impact is unclear, Labour leaning working class voters are less likely to have ID, but so are very Conservative leaning pensioners, so who knows. If a significant number of in-person voters are disenfranchised, then the Conservative leaning and already relatively high turnout postal voters could make an important difference on the margins.
Even if it makes little difference to the results if the 'bloodbath' fails to materialise for other reasons, such as recent poll tightening, then it's easy fodder for opposition parties to attack the Tories over the ID requirement.