One Liberal MP says he's signed letter asking Trudeau to resign, others remain mum

Liberal MP Sean Casey is the first to publicly confirm that he has signed a letter calling on Prime Minister Justin Trudeau to resign, arguing it would be in the best interests of the country to let someone else take the reins. 

As an internal revolt brews, few Liberal MPs who are not in the cabinet are publicly defending the prime minister. The upcoming caucus meeting on Wednesday appears to present the most serious challenge to Trudeau's leadership to date.