Quitting Labour and Conservative MPs need to decide where to position themselves if they want to keep their seats. Even then, it's going to be a slog.
A group of MPs has cited Brexit, anti-semitism and Corbynism more broadly as motivations to leave.
In this media landscape, who can blame the 35-year-old for stepping aside?
Chuka Umunna was not the person for the job, but neither is anyone else in contention.
Three parties must now choose new leaders. Labour has a number of candidates jockeying for position.
Names are already flying, but rushing an appointment would be a big mistake.
Labour's Chuka Umunna said Britain is lagging behind in terms of productivity. We got two academics to look at the facts.