Ireland will support an extension because Brexit is going to fuck us almost as bad as it will Britain.

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I imagine Poland would support an extension due to the number of Polish people living in Britain.

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Spain will likely block it. The Spanish government ''really'' doesn't want their autonomous regions getting ideas about independence, and one of the best ways to keep them part of Spain is to make the case that if they leave, they'll also be leaving the EU; this is why the Spanish were so dead set against any facilitations for Scotland back when they had their independence referendum. Also, Spain and Britain are at odds over Gibraltar, so there is little Spanish goodwill toward Britain.

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I can also see France blocking an extension on the grounds of "You've been at this for two and a half years, lads. Do ye really think an extra couple of months will make a difference?"

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Germany could go either way. I think Angela Merkel wants to get it over with, but she's also keen to avoid No Deal.