Carney and Poilievre can attack that problem immediately by stopping the personal attacks on each other.
I'm wary of anything that tries to "both sides" this. The Conservatives introduced this particular poison into our national politics, borrowing it from Republicans in the USA. Conservatives have become the party of negativity and hatred, with no positive proposals to improve the lives of ordinary Canadians. Conservatives have deliberately made themselves highly dependent on attack ads and fomenting distrust, suspicion and hatred. When other parties attack Poilievre they are responding to what he started. So let's start with holding Conservatives to the same standards as everyone else: a fully costed platform of actual policies, not just "trans people scary," fascist dogwhistles and "he's just like Justin."