Britain is scheduled to leave the European Union on March 29. If it is to avoid a chaotic withdrawal — one that could leave ports blocked and food and drugs running short — it needs an agreement spelling out divorce terms from the European Union. Once that critical document has been finalized, it must be approved by the European Parliament and by British lawmakers in a climactic vote. So time is running out.

For months, negotiations were deadlocked in Brussels while Prime Minister Theresa May’s divided Conservative Party was in turmoil, a reality underscored on Friday by the surprise resignation of Jo Johnson, a transport minister, over withdrawal from the bloc, known as Brexit.

So far Mrs. May has survived, inching her way toward an agreement, and she hopes for a breakthrough in the coming days. But the parties are not there yet, and Britain’s domestic politics are combustible. Here is the state of play.

What Is Happening Now

The prime minister has put her jittery cabinet on standby to endorse a deal she believes she can strike with the European Union. On Friday, she met with the French president, Emmanuel Macron, and talks with European officials will continue through the weekend.