When Emannuel Macron got elected President of France last year, he had some very big, very grand ideas about stabalising the euro, one of which was a common budget that would be used for fiscal transfers.
After ignoring his ideas for the best part of a year, Angela Merkel finally agreed to a small budget, because she needs Macron's help in the upcoming summit to push for a common migration policy.
However, the Franco-German stitch-up has angered twelve other countries who are adamant that there won't be a eurozone budget and that they won't transfer more power to the centre.
The eurozone has 19 members, and the Netherlands, Austria, Belgium, Denmark, Estonia, Finland, Ireland, Latvia, Lithuania, Luxembourg, Malta and Sweden have formed a block that doesn't want changes.
That leaves Spain, Portugal, Italy and Greece sitting on the sidelines watching. This group has a big enough population to swing the vote either way. Italy especially will be looking for some big concessions in return for going along with the Macron-Merkel plan. Such as a relaxation on national budget rules. Or perhaps some genuine help on migration. Or both.
What happens if the Macron-Merkel faction wins? Some very unhappy people in the Netherlands. Dutch Prime Minister Mark Rutte is on the record that with ally Britain leaving, the Dutch were going to have to fight more openly to resist more centralisation (rather than letting Britain doing all the fighting and everyone breathing a sigh of relief when they successfully blocked things). However, because the Netherlands is a much smaller country than Britain and doesn't have it's heft, it's finding it hard to push back at the centralisers.
At some point, if the Dutch get steam-rolled, expect them to start thinking about Nexit, especially if Brexit works out well.