There has been a very interesting series of phone calls in Labour circles in recent days. Members of Jeremy Corbyn’s team have been probing which MPs could serve under their man should the veteran left winger, as expected, be crowned party leader today.

The push has been for unity, for Labour to come together in the wake of a message from voters. But today's announcement is expected to kick off a series of sticky negotiations between Mr Corbyn and other Labour MPs.

Many remain shocked that the Islington MP, who has voted against his own party more than 500 times, will almost certainly now lead them as well as puzzled at how, practically, it would work.

Some within Labour are also, perhaps predictably, starting to look to the future and assess at what point Mr Corbyn could have to be replaced if it becomes apparent that the party under his leadership is failing to appeal to the wider voting public.

This is why 2017-18 could be very tense time indeed for Mr Corbyn, or whoever is elected Labour leader this morning.

It should be said, of course, that the Labour party is famously bad at getting rid of struggling leaders. However, some within the party believe that there are unavoidable outside pressures that could play a striking role.

Next year there are key elections in Scotland, Wales and London and to English councils.

Yesterday’s election of the left-wing MP Sadiq Khan as the party’s candidate in London means that the outcome of that contest will be watched more closely than it might have been otherwise.

However, some within Labour caution that next year is too early to draw conclusions and that failures in those elections would have other root causes.

“London’s always funny and Scotland, well, it is a nightmare for the party at the moment, “ one Labour source said.

However, if things are not starting to look good for the party by 2017, when there are council elections in Scotland, Wales and England, there is a feeling that that could legitimately be laid at the door of the new leader.

Opinion polls throughout will be watched closely, of course, though perhaps with less enthusiasm than before May’s General Election.

And there is another factor that some within Labour point to, for which David Cameron is responsible. The Prime Minister has pledged to reform Westminster seat boundaries.

Many Tories believe the move will, in one fell swoop, create an even bigger lead for their party over Labour in 2020. The plans could mean changes to the entire electoral map of the UK.

And it is this that has got some within Labour worried. They believe Labour MPs could be strong enough to resist any moves to de-select those not seen as left wing enough under the party's new direction.

But they fear that by later in this parliament the Boundary Commission reform process will mean MPs having to fight to represent what are essentially new seats. And that, some argue, could just bring any tensions between the new leader and some within his rank and file to a head.