Role of the PM and President -difference

Theme 1

Head of State role 

US 1

US President combines the head of gov and head of state in one office, both governing the country and representing it ceremonially.  

UK 1

In UK, Kings Charles III is the ceremonial head of state, whilst the PM is head of gov only.  

This gives the US president constitutional prestige and symbolic authority that the UK PM doesn't hold. 

Difference 1

Structural theory:  

-whether the Head of state and head of gov are fused or separated is fixed by constitutional design. 

Article II vests both roles in a single elected President, combining executive command with ceremonial national representation.  
UK Uncodified constitution preserves the Crown as a separate office pre-dating parliamentary democracy, so two roles cannot fuse.  

Difference: Constitutionally fused roles in single elected office (US) vs structurally separated crown and PM under constitutional monarchy (UK) 

Theme 2

Scope of military authority

US 2

The US president can deploy military force as Commander in chief without prior congressional approval, though the war powers resolutions 1973 limits deployment beyond 60 days. 

Trump’s June 2025 Iran Strikes proceeded without congressional authorisation showcasing President’s authority over military decision as commander in chief under article II.

UK 2

In the UK, 2013 commons vote against military action in Syria established a convention of parliamentary approval, which constrains the PM in practice.  

Difference 2

Cultural:  

-President as the leader of the country, and hold authority over emergency provision allow him to act unilaterally

UK PM constrianed by principle of parliamentary sovereignty

War powers are allocated by constitutional design in one system and by convention in the other.  

Theme 3

Role in legislative process (Veto vs agenda control) 

US 3

Trump can veto congressional bills, which can only be overridden by a two-thirds vote in both houses. Article I, Section 7 gives the President a constitutional veto, allowing him to block legislation passed by Congress. This power exists because the US Constitution is based on the principle of checks and balances. Since Congress and the President are institutionally separate, the veto was designed by the Founding Fathers to prevent Congress from becoming too powerful and to ensure that legislation receives scrutiny from another branch of government. However, because the President cannot control the congressional timetable, his influence over legislation is largely reactive. President Trump vetoed bipartisan Yemen resolution in 2019, with congress unable to override it.

UK 3

Starmer has no equivalent veto power. However, with a 174-seat Commons majority, he rarely needs one. As Prime Minister, Starmer benefits from government control of parliamentary business under Standing Order No. 14 and the whip system, allowing him to shape legislation before it reaches a vote. This makes his role more proactive, as he can influence the legislative agenda itself rather than simply responding to it.  -2022 Police crime sentencing and courts Act passage with limited opposition

Difference 3

Structural Theory 

The difference reflects the constitutional roles of the President and Prime Minister. 

In the US, the President is deliberately separated from Congress, so the Constitution grants a veto to give the executive a formal check on legislative power. The President’s role is therefore to review and potentially block legislation that Congress has already passed. 

In the UK, the Prime Minister is drawn from and leads the parliamentary majority. Because the executive already controls much of the legislative process, there is less need for a separate veto power. Instead, the Prime Minister’s role is to direct and manage the legislative agenda through Parliament.

Role Difference: 

US President: constitutional check on Congress through the veto power. 

UK Prime Minister: leader of Parliament who shapes legislation through majority control and agenda-setting.