If Mr Tsvangirai wins - and I am not suggesting that is either likely or certain - and if Zanu-PF claims he has done so because of foreign support, then Zanu-PF's justice minister will not accept the result.

BBC: Would Zanu-PF accept Tsvangirai as president?

Donors have promised to help finance a recovery plan but they are unlikely to release funds if a Zanu-PF minister is in charge.

BBC: MDC seeks new Zimbabwe election

Or he could try to woo Mr Makoni, if he came third, back into the ZANU-PF fold with a promise of forgiveness and high office, though that now seems implausible.

ECONOMIST: Could Robert Mugabe be unseated?