Well, it does seem that Ken has now made his mind up ahead of polling day this week.
The BBC reports that the Labour London Mayoral candidate has been out campaigning (for the TV cameras) with the anti-Labour Independent candidate for the Tower Hamlets Mayoralty, Lutfur Rahman.
Ken is a newly elected NEC member, the Labour governing body which usually throws party members out for less. The BBC reported that a Labour party spokesman tonight said only that the London Mayoral candidate backs Labour candidates everywhere, including in Tower Hamlets.
It is a very difficult race to call. Much may depend on the turnout. Ken's gesture could give important momentum to Rahman in the final week.
Yet there is very much all to play for.
The bookmakers Ladbrokes have Labour's Helal Abbas a slight favourite - at 4/7 on - with Lutfur Rahman at 5/4 against. The Conservatives - despite Ken's fear that they could come through the middle - are out at 33/1. (The local Labour party has been pretty solidly behind the Labour candidate Helal Abbas since the NEC decision).
As The Guardian's Dave Hill, who is continuing to offer the most comprehensive coverage, wrote at the start of the week:
This contest is a big deal. Winning control of the "Olympic borough" and its billion pound-plus budget is far more important than prevailing in most parliamentary by-elections and hugely important for Labour.
Anybody who wants to help back the Labour candidate in the last 48 hours can get in touch with the campaign office is at 349 Cambridge Heath Road, London, E2 9RA which is open for canvassing and leafleting from 10am until late every day until the election. You can ring 0207 729 6682 or email firstname.lastname@example.org for further details.