Labour MPs will choose a new member of the party's ruling National Executive Committee (NEC) today after kicking out an aide to Jeremy Corbyn.
Steve Rotheram was forced to step down after the parliamentary party voted overwhelmingly to bar Parliamentary Private Secretaries (PPS) from acting as the backbench representative on the body.
The MP for Liverpool Walton was already on the NEC when he was appointed as the leader's PPS in September.
A secret ballot is being held to fill the vacancy, with Shabana Mahmood - who quit the Labour frontbench when Mr Corbyn took charge - competing against George Howarth - who defied the leader to back bombing Islamic State (IS) in Syria.
An effort to get Mr Rotheram reinstated had been expected at Tuesday's NEC, where Mr Corbyn's allies have a slender majority.
However, the bid was apparently abandoned following legal advice that the Parliamentary Labour Party (PLP) was entitled to change its own standing orders.
A showdown over a controversial move to expand the NEC's terms of reference, potentially giving it more power over policy-making than the shadow cabinet, has also seemingly been delayed.