The decision of seven members of Parliament to quit the party on Monday and set up an independent caucus will in itself do little to alter the calculus in the House of Commons — they ignored the party line on Brexit anyway — but it could lead Labour Leader Jeremy Corbyn to review his strategy.
And if that happens, Prime Minister Theresa May could find herself fighting a strengthened campaign for a delay to the UK’s departure or a second referendum, which could embolden anti-Brexit rebels in her own party.
Labour has stopped short of backing a repeat plebiscite on leaving the EU, a policy that prompted some of those MPs to quit on Monday. So far Corbyn’s followers are doubling down on their support for the leader and his ambiguous Brexit policy of supporting the divorce while proposing closer ties to the EU.
Even so, Labour politicians who want a new referendum still hope Monday’s split might prompt Corbyn to switch policy and back a “people’s vote,” especially if supporters of the idea stay loyal.