Here's a look at what could happen next. BRITAIN LEAVES WITH A DEAL As it stands, Britain will cease to be a member of the EU at midnight Brussels time (11 p.m. London time) on Oct. 31. Johnson's government says it still thinks it can get Parliament's backing for the deal and pass the legislation needed to implement it in time to meet the deadline and leave in good order.
Two things are against it: time and numbers. It normally takes weeks or months for bills to pass through Parliament and become law. The government plans to publish its Brexit legislation, the Withdrawal Agreement Bill, on Monday evening, with the first round of debating and voting in the House of Commons on Tuesday. Officials hope to have the bill approved by the Commons by the end of this week, then send it to Parliament's upper chamber, the House of Lords and have it passed into law before the Oct. 31 deadline.
But there is no guarantee of majority support for the bill in Britain's fractious Parliament. Johnson's Conservatives hold just 288 of the 650 seats in the House of Commons, so he needs support from other parties and independent lawmakers to get the legislation through.
Opposition lawmakers also plan to seek amendments that could substantially alter the bill, for example by adding a requirement that the Brexit deal be put to voters in a new referendum. The government says such an amendment would wreck its legislation and it will withdraw the bill if it succeeds.
BRITAIN LEAVES WITHOUT A DEAL Even though a deal is uncertain, the chances Britain will crash out of the bloc on Oct. 31 without one have receded. Many British lawmakers fear a no-deal Brexit will cause gridlock at ports, shortages of some food and medicines and a deep recession. To avoid it, last month they passed a law compelling the government to ask the EU for a three-month delay to Brexit if the Halloween deadline was looming with no deal in place.
Johnson complied by sending the delay request on Saturday, while also stressing in a second letter that he personally did not want an extension. The EU says it is considering the request. The law also compels the British government to accept any extension the EU offers, so a no-deal Brexit will only happen if the bloc refuses.
Leaders of the 27 other EU countries — who must agree unanimously — are weary and frustrated at Britain's interminable Brexit melodrama. But they also want to avoid the economic pain that would come to both the U.K. and the bloc from a sudden and disruptive British exit. That means that, despite their grumbling, they are likely to grant a delay.
BREXIT IS DELAYED — AGAIN The third option is that Britain's departure, already delayed twice, will be postponed again. Johnson's oft-repeated vow that Britain will leave the EU on Oct. 31 "come what may" could go the same way as his predecessor Theresa May's insistence that the country would leave the bloc on March 29. No wonder May told lawmakers on Saturday that, watching the Brexit debate unfold, "I have a distinct sense of deja vu."
Brexit was supposed to happen in March, but with Britain's Parliament split over the departure terms the EU pushed back the deadline, first to April and then to October. If Johnson's deal is on track for approval, there could be a "technical extension" of a few weeks for the details to be hammered out and for the European Parliament to give its own consent to the agreement.
If the gridlock in Parliament continues, the EU could offer a longer delay but make it contingent on Britain holding a major event, such as a new referendum on Brexit or a general election. Both Johnson's Conservatives and opposition parties want to have an election that could shake up the parliamentary arithmetic and break the Brexit logjam. But a majority of lawmakers have to agree to an election — and so far they disagree on when to hold it.
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