Asked if she [Yvette Cooper] was worried if the party could split if he [Jeremy Corbyn] wins, she said: “I am, because I’m worried what’s happening at the moment, that the party does seem to be polarising between the different extremes and I don’t think that is the right thing to do.
“Partly, we want to hold our party together in order to win. Divided parties don’t win, but it’s actually much more than that. I just don’t think the extremes of the party are the right place to be and are true to our values and are true to the things we need to do to change the country for the future.”
BBC News Website 20 August 2015 : Labour Party could split under Jeremy Corbyn, Yvette Cooper says
It is (or was) of course open to someone to put themselves forward as a candidate not at the extremes. The fact that the centre appears vacant possibly says something about “Labour” in the 21st century.