Party system -similarity

Theme 1

Big tent main parties containing a range of views 

US 1

Two main parties in each country function as bit tent coalition that absorb wide range of ideological views inside a single organisation rather than letting them split into separate national parties.  

US dem:  

Progressives (Bernie Sanders, AOC)  

Centrist (Chuck Schumer) 

Blue dogs (Pete Geren) 

US Rep:  
MAGA populists (Trump, JD Vance) 
Fiscal conservatives  

Shrinking moderate republican (Mccain) 

UK 1

UK labour hold Blarite centrists (reeves, streeting), 

Soft left around (Burham, Lammy) 

Corbynites (corbyn, Raynor) 

Tory:  

One nation tories (Rory stewart) 

Right wing ERG (Jacob rees Mogg) 
post brexit populist (Kemi) 

Therefore the two main parties in each country are therefore broad churches that must accommodate organised faction inside their own structure. 

Similarity 1

Cultural theory:  

-named factions inside each main party  

Operate at identity bearing communities that demand recognition within the party.  

The shared cultural expectation in both systems is that ideological breath belongs inside the two main parties because exiting to start a new party would forfeit access to gov and the rewards that follow.  

 

Both party system treat the two main parties are legitimate homes for organised ideological factions.  

Theme 2

Difficulty for smaller parties to compete in national elections 

US 2

In both UK and US, smaller parties face significant barriers to winning national elections due to the FPTP single member districts, mechanically punish smaller parties whose vote is spread thinly across many seats rather than concentrated in winnable constituencies.  

 

In the US, third parties struggle to secure electoral votes or win seats in Congress.  

Example:   

Green party, libertarians  

-people vote as a protest vote   

In 2024 Presidential election, Green Party nominee Jill Stein received 0.56% of the national popular vote, as people voted green due to disagreements with Harris’ stance on Palestine (not strong enough 

UK 2

whilst in the UK, parties like the LibDems and SNP also find it challenging to compete against labour and the conservatives on a national scale. 

Example:  

In 2024 GE, Reform won 14% vote share but won 5 seat less than 1% seat share, demonstrate how geographically sparsely concentrated support can be punished despite high level vote share due to winner takes all outcome.  

Difference 2

Structural theory:  

Both system use FPTP at the national level, which systematically punish parties without concentrated geographical support, 

disadvantage smaller parties at national level, reinforcing a two-party dominance.  

Theme 3

Success of smaller parties are regional and local level 

US 3

Smaller or regional parties can achieve success at local or regional levels in both systems, even if they struggle nationally.  
In US, parties like the Libertarian party and the Green party have won some local seats,  

Example:  
2001–2022 

Minority (1/13 seats) 

Minneapolis City Council in Minnesota 

UK 3

whilst in the UK, regional parties like the SNP and Plaid Cymru have significant influence in Scotland and Wales, respectively. The SNP for example dominates Scottish parliament but holds less influence in Westminster. 

Example:  

In 2026, Scottish National Party has 60 MSPs, has near majority in Scottish parliament, controlling devolved legislative agenda, whilst only having 9 seat in Westminster.

Similarity 3

This is a similarity because smaller parties in both US and UK can succeed in localised areas, even if they lack significant power at national level.  

This is rational analysis, as it reflects how smaller parties adapt strategically to focus on regional influence where they have higher chances of success.