FILE - London Mayor Boris Johnson makes a statement outside his home in London, Feb. 21, 2016, announcing his support for the Leave campaign. The U.K. election in December 2019 was basically about one issue: Brexit. General elections in the U.K. are typically held in the spring or early summer. But in the fall of 2019, the recently-appointed Prime Minister Boris Johnson gambled on holding one on December 12, when most people just want to get ready for Christmas and would rather think of anything but politics. (AP Photo/Tim Ireland, File)
FILE - British Prime Minister Theresa May waits for the arrival of European Council President Donald Tusk prior to their bilateral meeting at an EU summit in Brussels, Belgium, Oct. 20, 2017. The U.K. election in December 2019 was basically about one issue: Brexit. General elections in the U.K. are typically held in the spring or early summer. But in the fall of 2019, the recently-appointed Prime Minister Boris Johnson gambled on holding one on December 12, when most people just want to get ready for Christmas and would rather think of anything but politics. (AP Photo/Geert Vanden Wijngaert, Pool)
FILE - Britain's Prime Minister David Cameron walks past a map of Europe on a screen as he walks away after making a speech on holding a referendum on staying in the European Union in London, Jan. 23, 2013. The U.K. election in December 2019 was basically about one issue: Brexit. General elections in the U.K. are typically held in the spring or early summer. But in the fall of 2019, the recently-appointed Prime Minister Boris Johnson gambled on holding one on December 12, when most people just want to get ready for Christmas and would rather think of anything but politics. (AP Photo/Matt Dunham, File)
FILE - Protestors are reflected in a large puddle as they wave European flags to demonstrate against Brexit in front of the Parliament in London, Dec. 3, 2018. The U.K. election in December 2019 was basically about one issue: Brexit. General elections in the U.K. are typically held in the spring or early summer. But in the fall of 2019, the recently-appointed Prime Minister Boris Johnson gambled on holding one on December 12, when most people just want to get ready for Christmas and would rather think of anything but politics. (AP Photo/Frank Augstein, File)
FILE - Britain's Prime Minister Boris Johnson drives a JCB through a symbolic wall with the Conservative Party slogan 'Get Brexit Done' in the digger bucket, during an election campaign event at the JCB manufacturing facility in Uttoxeter, England, Dec. 10, 2019. The U.K. election in December 2019 was basically about one issue: Brexit. General elections in the U.K. are typically held in the spring or early summer. But in the fall of 2019, the recently-appointed Prime Minister Boris Johnson gambled on holding one on Dec. 12, when most people just want to get ready for Christmas and would rather think of anything but politics. (Ben Stansall/Pool via AP, File)