Why are prime ministers often strongest just after an election?

Prime ministers are typically at their strongest immediately following an election because they often begin their term with a fresh mandate, high political prestige, and the full support of their parliamentary majority.1

In systems like the United Kingdom and other Westminster-style governments, a new prime minister holds significant authority to shape the government by selecting cabinet ministers, determining the legislative agenda, and managing the civil service. This initial period allows them to exert firm control over policy direction before the inevitable political challenges of governance—such as unpopular decisions, internal party divisions, or economic crises—begin to erode their influence and public standing.12

Over time, a prime minister's power may decay if the government becomes unpopular or if they face resistance from specialized policy communities and bureaucracies that possess expertise the leader may lack. Consequently, the post-election period represents a unique window of political capital where the prime minister's ability to act as a decisive chief executive is at its peak.12