Jeremy Corbyn is preparing to deliver a speech at Britain's biggest trade union on Tuesday, with Labour's ruling committee poised to decide whether he should be allowed to take part in the upcoming leadership race.
The Labour leader will speak at the Unite policy conference in Brighton, whilst the party's National Executive Committee (NEC) meets on London to decide whether he needs the nomination of 51 MPs and MEPs to stand in the contest.
The NEC has been presented with conflicting legal advice over Mr Corbyn's position.
Unite believe, as a sitting leader, he doesn't need the nominations, while Labour-commissioned analysis suggesting he does.
Mr Corbyn has said he will fight any exclusion from the ballot paper, but the anti-Corbyn camp are weighing up legal options if he is allowed to stand.
Meanwhile a YouGov poll on Monday, for the Election Data website, has found the Labour leader's union backing waning.
In the survey of 1,221 Unite trade union members, 63% of respondents said he was 'doing badly' as leader compared to 33% who said he was 'doing well'.
The poll is significant as 12 of the NEC seats are taken up by union representatives.
Meanwhile, Angela Eagle has met the nominations threshold and launched her election bid on Monday.
She insisted it was time Labour elected to have a woman as its leader, amid reports Owen Smith could launch a rival challenge.