With only a week remaining in the Labour leadership election, Owen Smith's campaign is putting all its efforts into winning over one group of voters: Labour-supporting union members. The campaign believes they are their candidate's last hope of shoring up his vote.
There's little chance Smith will be able to dethrone Corbyn before ballots close next Wednesday, and the focus is on ensuring the result is as close as possible.
As a result Smith's campaign is heavily targeting the approximately 200,000 trade union members who have registered to vote in the leadership election as Labour affiliates.
On Thursday the Smith campaign sent out a begging email to supporters in a bid to raise £50,000 by Monday to pay for a last-minute blitz of Facebook adverts and phone-banking targeted at union affiliate members.
Campaign sources believe this group are less likely to have already returned their ballot and are thought to be more welcoming of the anti-Corbyn message because they didn't necessarily join a union for party-political reasons.
"We think that [they] join a union not because they support Corbyn but for all the reasons you join a union," said one individual on the campaign.
The email sent by Heidi Alexander and Kate Green, the two Labour MPs chairing Smith's campaign, said: "If we can't hit the target [of £50,000], we can't reach them all, and that means we'll have less chance of beating Jeremy Corbyn."
"Many trade union members are at the sharp end of Tory cuts," Alexander and Green added. "They know Corbyn can't win, and we are having real success in persuading them of Owen's credentials. But we need your help if we are going to reach them all."
The email also suggests that Smith's leadership campaign has received donations from 6,399 Labour supporters – but tacitly acknowledges that the majority of people likely to cast a vote have already returned their ballots.
In addition, Smith used the entire opening statement of his appearance on Sky News' final Labour leadership hustings to make a direct pitch to the same trade union affiliate members.
"My message to all of those trade unionists is not enough of you voted last time," he said. "Not enough of you stepped up and took part in the process. If you want a Labour party that is back focused on the things that matter to you and your family then you have to get involved and you need to give me your vote."
Individuals on Smith's campaign insist that they are winning over many longstanding Labour members who voted for Corbyn in 2015. However, they admit they still face a struggle due to the substantial numbers of Corbyn supporters who joined the party after his initial victory in the leadership election, and the 180,000 people who paid £25 to sign up as a registered supporters.
YouGov polling conducted at the end of August found Corbyn was set for a clear victory, powered by strong support from the legions of £25 registered supporters. Smith performed better – though was still behind – among people who are full Labour party members and among union affiliates.
As a result some on the Smith campaign would be happy if they got 40% of the vote, given the current state of the electorate. This pitch to union affiliates could be one of their last attempts to get over that line.