The government's cannabis bill faces outright defeat in the Senate today if it can't secure enough support from members of the Red Chamber.

According to an agreed timetable, senators will hold a vote at second reading of the bill today. If the opposition Tories cobble together enough votes to defeat C-45, the legislation would be effectively dead — meaning the government would have to restart the entire legislative process in the House.

If that happens, a summer timeline for legalization becomes much less likely.