Prime Minister Justin Trudeau’s hold on power was threatened on Monday after the deputy prime minister who led Canada’s response to the first Trump administration resigned abruptly, in a stinging rebuke to the country’s leader.

A scathing resignation letter has triggered an unprecedented leadership crisis for Prime Minister Justin Trudeau. What triggered it, and can he hang on as leader?

The news shocked cabinet and caucus colleagues, senior Finance Department officials and the Prime Minister’s Office, and caused chaos among the Liberal ranks.