In the end, ten of John McDonnell's 16 supporters transferred their votes to Abbott but that still left her 12 votes short of the required 33 nominations. It was David Miliband's game-changing decision to back Abbott and urge his many supporters to do the same that secured her passage to the final round. MPs who had publicly backed his bid, including Stephen Twigg and Phil Woolas, rallied behind Abbott to ensure as diverse a field as possible.
I'm not sure that Miliband is Machiavellian enough to have considered this, but her place on the ballot will deprive Ed Balls and Ed Miliband of some of their left-wing support.
Meanwhile, Abbott's success has already divided opinion on the right of the party. Hazel Blears's former SpAd, Paul Richards, tweeted: "Some of us spent decades fighting the hard left. Now our MPs are falling over themselves to get the Campaign Group on the ballot. Crazy."
But other diehard New Labourites are pleased to see Abbott in the final round: it gives them a chance to inflict a decisive defeat on the left.
For many on the centre left, such as myself, Abbott's presence in the contest is a welcome development. It will force the other four nominees to test and refine their arguments against a candidate of the left. It will allow issues such as Afghanistan, privatisation and inequality to come to the fore. And it has ensured that the contest consists of more than four men with alarmingly similar backgrounds.
You'll be able to see Abbott and the four other candidates in action at tonight's New Statesman Labour leadership debate.