Aside from smearing Corbyn as a rabid anti-Semite, and otherwise defaming him, the forces backing Boris Johnson have played several dirty tricks to cut the Labour vote, as a good friend of mine explains:
First, one of the best UK election/parliament blogs is the YouTube channel “A Different Bias” by Phil Moorhouse. Check out one of his recent video commentaries.
Unfortunately if you don’t know about his channel, or his website https://www.patreon.com/adifferentbias, they’re nearly impossible to find, as Google has buried them.
Moorhouse describes the dire situation of UK expats living abroad, unable to vote in their home country’s General Election. Although still eligible to vote, they have not received their postal ballots in time to send them in by the deadline, as happened with the May 2016 election:
British Citizens Not Allowed to Vote in the General Election
There also seems to be some truth to claims of Labour postal ballots being delivered/counted late. Apparently there were hundreds of thousand of postal ballots that never got delivered or were delivered too late, for example on the day of the election, preventing many UK citizens living abroad to to cast their vote:
I’ve also learned that approx. 60% of the 5 million UK citizens living abroad are unable to cast a vote in the Dec 2019 General Election because of a rule stating that a UK citizen who has lived abroad for over 15 years becomes ineligible, as described in this article below:
It’s estimated just under five million Britons are now living overseas, either in retirement or for work, with around 60% now denied the human right to cast a vote in one of the most crucial general elections since WWII. Spain is home to many thousands affected by this cruel rule, with the result likely to destroy their chosen lives unless the Spanish government allows them an unconditional stay. Even should this happen, British expats now making regular visits to their extended families still in the UK may well be hamstrung by the cost and bureaucracy involved in a short-term return to the home country followed by re-entry into Spain..Some articles on the anti-Labour disinformation campaign:
Apparently the Tories are polling ahead of Labour but things could shift if enough voters decide to change their vote at the last minute.