After the Labour Party refused to back his call for a Dec. 12 election, Mr. Johnson immediately said he would introduce a bill to circumvent the 2011 law that requires a two-thirds majority in Parliament to schedule an election, so that only a simple majority would be needed.

Hopes for a breakthrough: The centrist and pro-European Liberal Democrats and the Scottish National Party indicated this weekend they would be prepared to vote in favor of a December election. Still, the election is not a guarantee.

Quotable: “We’re all like Charlie Brown,” Mr. Johnson said, “endlessly running up to kick that ball, only to have Parliament pull it away again.”