Andrew Scheer says he should be PM if Conservatives win the most seats. It's not that simple - 2019-10-17
In recent elections, the party that won the most seats has ended up forming the government. However, in a minority situation, things could get interesting.
If no party wins a clear majority in the House of Commons next week, Trudeau will still be the prime minister. But if his Liberals have won fewer seats than the Conservatives, he will face a choice: he can attempt to marshal support from MPs of other parties, either on a vote-by vote basis or through a formal coalition, or he can concede defeat, as Paul Martin did after Stephen Harper's Conservatives won a plurality of seats in the 2006 federal election.
If Trudeau were to step down, the governor general would then either invite another party to attempt to form a government, or call another election.