Power versus Ideology: Political Group Switching in the European Parliament

• Published date: 01 November 2018
• Author: Simon Hix,Abdul Noury
• Date: 01 November 2018
• DOI: http://doi.org/10.1111/lsq.12202

SIMON HIX

London School of Economics and Political Science

ABDUL NOURY

New York University, Abu Dhabi

Power versus Ideology: Political

Group Switching in the European

Parliament

Why do legislators switch party? We seek to identify whether “party switching”

is mainly determined by power (to join a more influential party) or ideology (to join a

party with closer policy goals). We focus on the 557 cases of political group switching

in the European Parliament between 1979 and 2014. We find that most of these cases

were from smaller, more marginal, and oppositional groups, to larger, more pivotal, and

governing groups. Nevertheless, we also find that ideological congruence (between an

MEP and his or her prospective group) was an important determinant of political group

switching.

Do politicians ultimately seek power, or are they primarily driven

by their ideological convictions? This is an age-old debate in political

science. On one side are scholars like William Riker, who assume that

politicians’ actions are ultimately driven by their desire to maximize their

inf‌luence over political outcomes (e.g., Riker 1962). On the other side

are scholars like Keith Poole, who believe that politicians “die in their

ideological boots” (Poole 2007; Poole and Rosenthal 1997, 100). In this

article, we seek to shed some light on this debate by focusing on the

determinants of why elected politicians switch between political parties.

Do politicians change parties to gain more power or to join their ideolog-

ically similar colleagues?

Most cases of politicians switching between political parties have

happened in the legislative arena rather than in the electoral arena (cf. La

Palombara and Weiner 1966). One interesting case of such “party

switching” is by the Members of the European Parliament (MEPs). The

European Parliament is now a powerful legislative chamber in European

Union (EU) decision making; more akin to the US Congress in the US

“separated-powers” system of government than legislatures in “fused-

powers” parliamentary systems at the national level in Europe and

LEGISLATIVE STUDIES QUARTERLY, 43, 4, No vember 2018

DOI: 10.1111/lsq.12202

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elsewhere. As in the US Congress, legislative majorities in the European

Parliament have to be built issue by issue because neither the EU Com-

mission nor the EU governments command an in-built majority in the

chamber to push bills through. This gives the “political groups” in the

European Parliament signif‌icant legislative power, broadly in proportion

to their size in chamber.

The European Parliament is a good case for focusing in on party

switching because legislative bargaining inside the parliament is largely

isolated from electoral incentives. In most countries in the EU, European

Parliament elections are “national second-order contests”—fought on

the performance of national politicians and parties rather than on the per-

formance of the MEPs or the political groups inside the European

Parliament (Hix and Marsh 2007; Reif and Schmitt 1980).

1

As a result,

internal policy (ideological) and career (power) incentives inside the

European Parliament are stronger drivers of political group switching

than external electoral incentives. This enables us to isolate internal

power and ideological factors in MEPs’ political group switching deci-

sions, which is often not the case in studies of party switching in other

democratic parliaments.

2

Switching political groups inside the European Parliament also has

relatively low transaction costs compared to some other legislatures. In

addition to the low likelihood of domestic electoral punishment for

switching parties inside the chamber, power inside the political groups

(such as committee assignments or leadership positions) is allocated

broadly in proportion to the size of each national “party delegation” in a

group (Benedetto 2007). This means that MEPs can reasonably and

accurately calculate the likely costs and benef‌its of switching when con-

sidering whether to stay in a particular political group or switch to

another one.

Out of 5,179 individual MEPs in the seven elected sessions of the

European Parliament between 1979 and 2014, 504 switched political

group at least once (almost 10%). At face value, this might seem like a

high proportion of the members of a democratic parliament in a 35-year

period. In most established democracies, unlike new democracies,

switching between political parties is a rare occurrence. Yet, given the

lack of potential electoral punishment of switching, the low transaction

costs of joining another group, and the potentially high policy or career

incentives to change groups, the fact that almost 90% of MEPs remained

in the same political group for the duration of their careers in the Euro-

pean Parliament suggests that the political groups in the European

Parliament do represent a certain equilibrium of the individual-level and

collective incentives of the MEPs.

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The rest of the article is organized as follows. We f‌irst discuss the

existing literature on party switching in legislatures before setting out

our own theoretical understanding of why some members in the Euro-

pean Parliament would want to switch political group. In short, we see

each European Parliament election every f‌ive years as an exogenous

shock to the party system equilibrium inside the chamber: adding new

MEPs and new national party delegations and usually new EU member

states too; changing the balance of power between the existing political

groups; and changing the balance of power between the national parties

within the political groups. Individual MEPs and national parties then

consider their policy goals and strategic career incentives and decide

whether to stay or switch political groups, until a new equilibrium

emerges. A key reason why some MEPs want to switch is related to

learning. MEPs learn over time whether their incentives are compatible

with their existing political groups or whether they would be better off

joining a new political group. However, MEPs are likely to think care-

fully before giving up the policy and off‌ice benef‌its they derive from

their existing political group.

We test these ideas in a statistical model of political group switch-

ing for the entire history of the European Parliament. This will allow us

to look at time-series dimension of the data and explore how switching

has evolved as the European Parliament has grown in size and become

more powerful. We use roll-call voting data to measure actual diver-

gence between individual MEPs and their groups’ positions in votes.

Using a pooled logit model, we f‌irst compare switchers to nonswitchers

and show that power and ideology are important determinants of switch-

ing. Our conditional logit model then indicates that both power and

ideology are also important determinants of political “migration” in the

European Parliament. The “power difference” between two prospective

political groups an MEP could belong to has a positive effect on the

probability of switching, meaning that MEPs move to more powerful

political groups. MEPs are also likely to switch to ideologically closer

political groups. Our results also indicate that loyalty, a measure of how

often prior to switching a member votes with his or her party l eader,

decreases the probability of switching, indicating that loyal members are

less likely to switch group.

General Literature on Legislative Party Switching

In a comprehensive review of existing research on legislative party

switching, Carol Mershon points out that a common feature of most

research is that “politicians switch in search of both off‌ice and policy

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