The past decade has seen extreme flux in British electoral politics. The parties that have traditionally dominated the party system—the Conservatives, Labour, and (to a lesser extent) Liberal Democrats—received their lowest-ever joint vote share in the 2015 election. But the subsequent election, just two years later, returned the largest two-party share since 1970. Measured in terms of “volatility”—the index introduced by Mogens Pedersen (“The Dynamics of European Party Systems,” European Journal of Political Research, 1979) to capture electoral churn—these were the most dramatic shifts since the Great Depression. Electoral Shocks, by Edward Fieldhouse and colleagues, analyzes this period of high turbulence, developing an account of why elections and party competition in Britain today seem less predictable than they were in the past.

The book presents a novel theory of “electoral shocks,” defined as “disturbances that have the ability to lead to substantial and dramatic increases in vote-switching and therefore to changes in the party system” (p. 31). The period of turbulence was shaped by five such shocks: rising immigration from 2004 onward, the Global Financial Crisis beginning in 2008, the coalition government of the Conservatives and Liberal Democrats in power from 2010 until 2015, the Scottish independence referendum of 2014, and the European Union (“Brexit”) referendum of 2016. These shocks differed in important ways. Some unfolded over time (e.g., rising immigration), whereas others came to a head in a single event (e.g., Brexit referendum). Some shocks can be traced to elites’ decisions (e.g., the formation of the coalition government), whereas others were more exogenous, with origins beyond the party system (e.g., the Global Financial Crisis). But all the shocks transformed public opinion through their effects either on issue salience or on perceptions of the parties’ identities or competence.

The authors argue that although a party system can be shaken up by such events, this need not be the case. A shock’s effects depend not only on how elites respond to it but also on how firmly the system’s fundamentals are anchored. Party identification, in particular, “may provide some insulation from electoral shocks” (p. 45). But party identification has been declining in Britain, as in many other countries, so this vital buffer to events with shock potential has weakened. The shocks of the contemporary era should therefore not be regarded as being more intense than somewhat similar events in the past, nor have they occurred with greater frequency. What is different, the authors assert, is that the British party system has become significantly more susceptible to change.

Multiple waves of panel data from the British Election Study (BES) are used to validate this argument, beginning with the evidence of dealignment. The authors report that in the four elections up to and including the 2017 election, 60% of voters switched parties at least once. In the 1960s, Butler and Stokes (Political Change in Britain, 1969) identified 13% of British electors as swing voters. So the decline in partisan commitment has been significant, but it is difficult to explain. It is not well accounted for by the decline of class divisions, the parties’ ideological convergence, or growing voter sophistication, which leaves the root cause “somewhat elusive” (p. 73). The book’s empirical analysis then goes on to explore the effects of the shocks on this more fickle electorate. For instance, the first shock, the Labour government’s 2004 decision to allow unrestricted immigration from 10 new accession states to the European Union, increased the salience of immigration as the migrant flows greatly exceeded the government’s expectations. Labour’s reputation on this issue was severely tarnished as a result, but future Conservative governments also struggled to reduce immigration. Consequently, a Eurosceptic, anti-immigration space in public opinion opened up, which was filled by the populist United Kingdom Independence Party (UKIP). These developments ultimately laid the ground for the final shock, the Brexit referendum of 2016. Its fallout included the return to a high level of major-party voting at the 2017 election, driven by a new cultural axis centred on immigration and liberal/authoritarian values.

Electoral Shocks is a major and impressive contribution to British and comparative research on elections, public opinion, and parties. Its theoretical framework highlights macroevents in a way that is unusual in these literatures, which tend to downplay such factors to focus on individual-level processes. But its account of electoral shocks is embedded and unpacked within a rigorous discussion of public-opinion dynamics. This design will be valuable for research on other countries, to understand their spells of political turbulence. The grounding of the book in BES data connects it with the many other studies that have used this resource, especially Butler and Stokes (1969). That pioneering book analyzed the gradual replacement of the Liberals by Labour during the interwar years. Comparing this long-term process of change with the period of turbulence explored in Electoral Shocks, it becomes clear not only how much British politics has transformed between the publication of these two books but also why “political change” needs to be studied across multiple levels and dimensions to make sense of what has happened in that time. Electoral Shocks brings key insights and tools to this project.

For all its merits, the book leaves largely unsettled the question of why dealignment has occurred. Future researchers will no doubt be drawn to this puzzle. The theorization of “electoral shocks” is rich and persuasive, but it will be interesting to see how the shocks it identifies appear when they are farther away in time. It may be that one shock (e.g., Brexit) will stand out as the truly decisive one during this turbulent period, whereas others (e.g., Conservative-Liberal coalition government) may eventually seem more minor. The book’s framework will also be useful for analyses of the future of electoral politics in Britain. One potentially significant development, flagged in the book’s conclusion, is the end of elections to the European parliament because of Brexit. These elections have often been a stepping stone for minor parties, including UKIP, giving them a national platform and a source of funding (if they win seats in the European Parliament). Without this springboard, and with the major parties having incorporated cultural issues into their platforms and competitive relations, the opportunities for minor parties (with the notable exception of the Scottish Nationalist Party) may well have shrunk. This, in turn, opens up the possibility that competitive dynamics among the major parties may actually stabilize despite the dealignment trend discussed in Electoral Shocks.