Patrick Maguire is the New Statesman's political correspondent.
Despite the resignation of Ian Austin, some believe the splitters have made the internal battle easier.
Corbyn is under pressure to back a second referendum to prevent further defections. But that alone won’t stabilise the party.
The group would support the government in a confidence and supply arrangement if given a second referendum.
More defections will only make it more difficult for members to dismiss political differences by insisting their new club is pre- or post-policy.
Has lingering imperial nostalgia found new expression through Brexit?
“There would have to be a sea change to lead me to believe Jews had a safe place in the party.”
The defections of Anna Soubry, Sarah Wollaston and Heidi Allen could make or break the new party.
The Enfield North MP accuses Jeremy Corbyn of “presiding over a culture of anti-semitism and hatred of Israel”.
Ministers want a codicil, but the ERG leadership is making clear that nothing less than its removal will do. Just how many MPs agree with their analysis will determine how easily May's deal can pass.
The Labour splitters describe their not-quite-new party in their own words.