Degree of internal unity within parties -similarity

Theme 1

Presence of faction within major parties

US 1

Both parties contain factions.
democrats range from progressives (Bernie Sanders, AOC) to Centrists (Obama, Biden).
republicans are dominated by MAGA populism (Trump JD Vance, Marjorie Taylor Greene) with shirking traditional conservative minority (Collins, Murkowski -RINOs : who voted to support installment of Ketanji brown jackson, voted alongside John Mccain in rejection of 2017 skinny repeal.American Health Care Act of 2017)

UK 1

UK conservative party includes both centrist one nation members like Boris Johnson, Thatcherites, and hardline Brexiteers from ERG like Jacob Rees-Mogg, while the labour party has socialist factions led by Jeremy Corbyn known as Old Labour and more centrist factions aligned with Starmer and Blair, known as New Labour.  

Mini1

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 US and UK parties house a variety of ideological perspectives, reflects broader societal values and cultural divides, leading to factionalism/internal party tensions. 

Theme 2

Pressure for unity on key votes

US 2

Both UK and US parties enforce unity on significant legislative votes.  

In the US, party leaders work to secure votes on critical issues, esp when it comes to passage of key manifesto commitments, where party cohesion is essential.  

Example:  

One Big Beautiful Bill Act 2025, combining permanent tax cuts, defence spending, etc 

Passed house 214-218 overcoming unanimous democrat opposition and Passed senate 51-50 with JD Vance casting tie breaking vote. 

UK 2

In UK, party discipline is similarly strong on important votes, especially on critical legislative decisions like Brexit. 

Example:  

Tory members under three line whip with threat of disciplinary action under Boris Johnson cabinet (having already removed whip from 21Mps who rebelled against Bojo’s no deal brexit), resulting in smooth passage of internal market Act 2020 despite concerns over its impact on devolution and consistent opposition from devolved legislature. 

Mini 2

Rational choice theory:  

-legislators weight the upside career prospects of compliance with the party whip (committee placement US, ministerial advancement UK) against the downside of rebellion (primary challenge from extremist candidate US, withdrawal of whip UK)  

When the leadership controls both upside and downside in the same hands, rational members align even on bills they privately oppose.  

The similarity here is the same cost benefit logic governs party discipline in both system. 

Theme 3

Internal discontent can lead to tension with the leadership 

US3

In both systems, disunity can trigger leadership challenges or significant shifts within the party.  

In US, internal opposition affects party dynamics and has impacted the influence of leaders like Trump, where factions like the traditional conservatives and moderates have occasionally resisted his influence. 

Example:  

In a 219 to 211 vote, six Republican lawmakers joined Democrats to back a resolution that seeks to end the tariffs Trump imposed on Canada in 2025. 

One of them was republican representative Thomas Massie from Kentucky, a member of fiscal conservative faction of republican party. 

UK 3

In UK, party leaders face moral challenges more frequently, as seen with Conservative leaders like Bojo, who faced internal pressure that eventually led to their resignations. 

Example:  

The Confidence Vote (June 2022): Following the "Partygate" scandal and mounting pressure, Conservative MPs held a vote on his leadership. Johnson won the vote , while 41% voted no confidence in his leadership.  the large rebellion severely weakened his authority, and further wave of resignation of big beasts like Sunak, forced his resignation.  

Mini 3

This is a similarity because internal divisions can lead to leadership challenges or power struggles within both US and UK parties.  

This is rational analysis as it focuses on how party members act in their interests, initiating leadership challenges when dissatisfaction with leadership grows.