2-Examine the degree of internal unity within parties in the UK and US

Overall Point:
UK parties exhibit stronger internal unity than US parties because of stronger party discipline mechanisms.
Explanation:
In the UK, the whip system and the fusion of powers between the executive and legislature mean MPs have greater incentives to follow the party line, especially if they seek promotion.
UK Evidence:
In 2019, Boris Johnson removed the whip from 21 Tory MPs who voted against his Brexit deal—an extreme but telling example of enforcing party unity. Labour MPs are frequently whipped and punished for rebellion (e.g. Jeremy Corbyn suspended for breaking party line on antisemitism).
Explanation:
By contrast, US parties are much looser coalitions. The separation of powers gives legislators independence from the executive and their party leadership, reducing enforcement capacity.
US Evidence:
Joe Manchin (D-WV) and Kyrsten Sinema (I-AZ, formerly D) often opposed Biden’s agenda despite Democratic control of Congress, e.g. blocking filibuster reform and parts of Build Back Better. Congressional voting records show frequent cross-party votes, especially on economic or state-based issues.
Comparative Theory (Structural):
The UK’s structural centralisation and strong executive lead to higher party unity, while the US system—with its checks and balances—deliberately empowers individuals, weakening party cohesion.

Overall Point:
US parties are ideologically broad “umbrella coalitions,” whereas UK parties tend to have clearer ideological identities, leading to greater cohesion.
Explanation:
The First-Past-The-Post system in both countries encourages broad coalitions, but in the US, the lack of formal party membership and looser leadership control intensifies internal ideological division.
UK Evidence:
Despite factionalism (e.g. Momentum vs. moderates in Labour), UK parties usually campaign on coherent platforms and hold members to a common manifesto (e.g. Sunak’s 2024 platform or Corbyn’s 2017 pledges). MPs risk deselection if too rebellious.
US Evidence:
US parties include stark ideological divides: the Democrats range from democratic socialists like AOC to moderates like Josh Gottheimer; the Republicans include moderates like Susan Collins and hard-right figures like Marjorie Taylor Greene. Party leadership often struggles to manage this (e.g. McCarthy’s short-lived Speakership in 2023).
Comparative Theory (Rational):
US politicians are rational actors representing local/state interests first due to primaries and re-election incentives. In the UK, rational actors prioritise party unity for career progression and electoral safety due to stronger centralised candidate control.

Overall Point:
US primaries reduce internal unity by encouraging personalised campaigning and outsider candidates, while UK candidate selection is centralised, promoting loyalty.
Explanation:
In the US, candidates are chosen through open or closed primaries, often without party leadership control, allowing ideologically extreme or independent-minded candidates to win nomination.
UK Evidence:
In the UK, party leaderships maintain tight control over candidate selection and deselection, ensuring ideological alignment and loyalty. For example, CCHQ can veto candidates; Labour’s NEC blocked left-wing candidates from standing in safe seats.
US Evidence:
Trump’s rise in 2016 illustrates how primary systems allow anti-establishment figures to capture a party despite elite opposition. Similarly, progressive Democrats have ousted incumbents in primaries (e.g. AOC defeating Joe Crowley in 2018).
Comparative Theory (Individual):
In the US, individual politicians can build independent brands and voter bases, leading to weaker unity. In the UK, individualism is structurally discouraged by centralised selection and party discipline, promoting stronger unity.