There is a significant disconnect between the common wisdom surrounding pork barrel spending and what the evidence shows. The conventional wisdom among journalists and politicians is that pork barrel spending—money that members of Congress (and other politicians) divert to their districts for local spending projects—helps all Congress members win reelection. This belief also shows up in academic treatments of the subject: the classic distributive spending model is rooted in the twin assumptions that pork helps all members get reelected, which leads all members to pursue spending for their districts equally. However, the conventional wisdom is at odds with the evidence coming out of decades of studies that examine how pork barrel spending influences members’ reelection prospects. When studies examine Democratic and Republican Congress members separately, they universally find that pork helps Democratic members win reelection, but does not help Republicans (e.g., Bruce Cain, John Ferejohn, and Morris Fiorina, The Personal Vote: Constituency Service and Electoral Independence, 1987; Patrick Sellers, “Fiscal Consistency and Federal District Spending in Congressional Elections,” American Journal of Political Science 41, 1997; Jeffrey Lazarus and Shauna Reilly, “The Electoral Benefits of Distributive Spending.” Political Research Quarterly 63, 2010). Andrew Sidman’s recent book on pork barrel spending offers the fullest exploration of this partisan asymmetry to date.

Following these earlier studies, Sidman argues that the pork barrel is inherently ideological. Liberal voters are typically proponents of government spending in general and support the government’s role as an equalizing agent across society. Thus most liberals are inclined to rate their members of Congress more highly if they bring federal spending back to the district. In contrast, conservative voters tend to support fewer specific government programs and prefer lower levels of government spending overall. These voters are less likely to see government spending on local projects as a good thing, and on the whole, they do not reward members for procuring such projects.

Yet conservative voters do favor one form of government spending: the contingent liability (Kenneth N. Bickers and Robert M. Stein, “The Congressional Pork Barrel in a Republican Era,” Journal of Politics 62, 2000). Contingent liabilities are government guarantees of risk, typically in the form of guaranteeing a bank loan or backing an insurance policy. For example, the government guarantees certain small business loans, which makes them less risky for banks and results in more small businesses being supported by these loans. This type of spending program is more in line with the conservative political outlook than traditional distributive spending on two counts. First, the business taking out the loan still succeeds or fails on its own merits (echoing conservative calls for “equality of opportunity,” rather than “equality of outcome”). Second, contingent liabilities square with conservative preferences for lower spending, because the government only spends money for loans that default. Thus public outlays on these programs are limited. As a result, contingent liabilities are sometimes called “Republican pork.”

The heart of Sidman’s argument is that these ideological distinctions have significant partisan effects. Liberal voters reward their members for procuring federal spending; since most liberal voters are represented by Democrats, this results in higher vote shares for Democratic members. As for Republicans, on the one hand, conservative voters do not reward their Congress members for the spending they bring home; indeed, some Republican members actually pay an electoral penalty for procuring federal spending. On the other hand, Republican members are rewarded electorally for procuring contingent liabilities for their districts, and those programs are less likely to help Democrats.

A consideration that Sidman adds, and the theoretical concept that is most original to the book, is that these ideological cues produce more consistent electoral effects when political polarization is high. When polarization is low, the existence of conservative Democrats and liberal Republicans attenuates the partisan effect that pork barrel spending has on elections: some part of the Democratic electorate prefers low spending, and some part of the Republican electorate prefers high spending. Thus, the ideological nature of pork barrel spending is somewhat obscured. However, during times of high polarization, conservative voters are more or less all Republicans, and liberals are more or less all Democrats. This means the ideological cues voters respond to—including cues coming from government spending projects—map almost perfectly onto party, which gives these cues their maximum impact on electoral outcomes.

Sidman tests this theory with a variety of data, starting with dividing pork barrel spending into ideologically significant categories. He begins with three categories: public works projects, such as spending on road and bridges (the prototypical, historically original, pork barrel spending), contingent liabilities, and military spending. An initial examination confirms that members’ pursuit of each type of project is conditional on party, ideology, and polarization in the ways suggested by the earlier discussion: Democratic members are more likely to pursue public works spending, and Republican members are more likely to pursue contingent liabilities. The ideology of military spending is less clear than the other two categories, so throughout the rest of the book Sidman focuses on contingent liabilities and public works spending. A separate individual-level examination of voter attitudes also confirms that conservative voters are less receptive to spending than are liberal voters, and they also are more likely to hold this view when they live in a district with high levels of distributive spending.

The bulk of the empirical examination focuses on public works projects’ and contingent liabilities’ separate effects on a wide variety of electorally related outcomes. These outcomes include Congress members’ election returns, individual-level vote choice, likelihood of drawing opponents in primary elections and quality challengers in general elections, and campaign fundraising. As with all wide-ranging empirical investigations, results are messy, and not all hypotheses are supported by the data. But in general the results are consistent: high levels of traditional distributive spending (i.e., public works spending) are associated with liberal voters being more likely to vote for their incumbent representative and Democratic members doing well when seeking reelection. Conversely, high levels of spending are associated with conservative voters being slightly less likely to vote for their incumbent member than when spending is lower; as a result, Republican members do not receive the same benefit from distributive spending. Indeed, such spending can actually hurt Republicans; for example, in chapter 5 Sidman finds that high pork barrel Republicans are more likely to draw a primary election challenger. Conversely, over the course of Sidman’s investigations, he finds that contingent liabilities tend not to affect Democrats’ reelection prospects but do significantly help Republicans by increasing their levels of campaign spending (chapter 6). And all of these trends are accentuated when polarization is high.

All told, this book is a significant addition to the study of pork barrel politics. Many of the theoretical concepts that Sidman discusses originate elsewhere in the literature, but the book brings them all together in one place for the first time and adds the novel insight that polarization conditions the partisan response to pork barrel spending. As well, this book provides by far the broadest empirical examination of pork barrel spending’s influence on electoral outcomes to date. This empirical work both confirms previous findings and provides us with new insights into the role that pork barrel spending plays in congressional elections. Thus, the book is an important new resource for all who wish to understand how pork barrel spending works.