Welsh woes for Labour?

Are we on the brink of a political earthquake in Wales? Newsnight is live at the Caerphilly by-election, which could provide an almighty political headache for the prime minister. Could it signal the end of two-party politics? As the east wing of the White House is torn down and No Kings protestors take to the streets, is President Trump actually keen to be king of America? With Nick Watt.