Can Owen Smith do it?
In the last two weeks Owen Smith has gone from someone who one MP described as "just playing games" to being the official challenger to Jeremy Corbyn.
Can he pull off a far bigger ask of actually beating him, and demolishing Mr Corbyn's mountain of membership support?
On his side is, finally perhaps, unity among the vast majority of Labour MPs and MEPs.
Angela Eagle dropped out with dignity so that there would be only one candidate. Owen Smith was warm in his tribute to her tonight and dropped heavy hints about campaigning side by side with her in the next two months to smooth the way for senior MPs to work together.
It's understood that he has promised her the position of shadow chancellor if he wins the post. And despite some disquiet inside the party about not fielding a female candidate, in most quarters there is relief and a new focus now there is only one candidate and the race is under way.
Yet if the contest were held tomorrow it's highly likely that Mr Corbyn would win again, setting off an unpredictable chain of events that might lead to the party's end. MPs have withdrawn their support, made it clear that they don't think he is up to the job, former ministers, former party leaders, some of his former supporters have made it abundantly clear they don't think he is up to the job.
Yet still he has hung on, and his team are as determined to battle on through a long, hot summer.
As I write, they feel sure the core of the membership is on their side.
There is however from MPs and even from some union sources, anecdotal evidence that his party support is shakier than it once was. One union boss told me "it has to be Owen".
But last summer Mr Corbyn and his team set off something not seen for many years, a political excitement among some people on the left that propelled him into office.
Turning that around, not least without causing resentment and disillusionment, is a massive task. But by manoeuvring himself onto the ballot Mr Smith has shown he has the energy and ambition to give it a damn good try.