So at present, the PM is legally obligated to request an extension from the EU before October 31st if a deal has not been reached with the EU and accepted by parliament. However, Johnson insists he will "under no circumstances" extend the deadline.
So, what outcomes are now possible?
A) A deal is reached with the EU and accepted by Parliament. Seems unlikely, given that Theresa May's deal was rejected by Parliament and the EU says it will not rewrite parts of the deal to suit the UK.
B) General Election called under the Fixed Term Parliaments Act. Could provide a majority for a way forward (be it a deal, second referendum, or no-deal). However, it requires a 2/3 majority in parliament, and most opposition parties have agreed that no-deal must be blocked before an election proceeds.
C) Government calls a confidence vote in itself, loses on purpose, triggers an election. This is the only way for the government to trigger an election without the 2/3 majority mentioned above: this method requires only a simple majority. Considered the "nuclear option" given how ludicrous it looks for a ruling party to declare that it doesn't have confidence in itself.
D) Second referendum. Unlikely, since the Conservatives are dead against. Supported by Labour, the Lib Dems, and others, though. More likely that A, B or C at this point.
E) Johnson ignores the law requiring him to seek an extension, and just refuses to do so. Places him in contempt of Court. Incredibly, several Conservatives have given ambiguous answers when asked whether the government would comply with the law. Johnson may be jailed if this comes to pass, according to legal advice.
F) Johnson resigns to avoid asking for an extension. Conventionally, The Queen would be expected to then ask the leader of the opposition to attempt to form a government.
G) Johnson swallows his promises and requests an extension. Given how unequivocal he has been on this point, I imagine this would severely damage the Conservatives at the ballot box.
H) Extreme outlier possibility... the British government provokes the EU into kicking them out, thereby bypassing Parliament and leaving without a deal. One possible method for such provocation could be refusing to name a British commissioner. Even this would be extremely unlikely to actually succeed, however, and is the least likely possibility.
