I believe that if 2 Prime Ministers leave office, either by resegnation or removal by their party, within 1 parliamentary term, the second Prime Minister leaving office should automatically trigger a general election.
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I believe that this policy would be essential for democracy. Circumstances may mean that the party in power changing their leader would be the best thing to do. However, I believe that a second change of Prime Minister in the same parliamentary term would leave no mandate for the third leader and question the majority party's suitability to govern.
The decision to continue with that party or elect another should therefore be put back to the people.