Today’s argument takes the form of a reductio ad absurdum.
premise 1: Canada’s newspaper of record would only endorse a centrist political party.
premise 2: The Globe & Mail is Canada’s newspaper of record.
premise 3: The Globe & Mail endorsed the Conservatives.
Conclusion: the Conservatives are, therefore, a centrist political party.
Since the conclusion is absurd, and the argument form is valid, at least one of the premises must be false. But which one?