Swing states are the Holy Grail of American presidential campaigns. Target the right ones in a given election and victory will likely be yours. For students of American politics, the major challenge is to explain this phenomenon. What gives some states “swing” status? Or as the subtitle of this timely volume tantalizingly puts it, “Why Only Ten States Matter.” This is a team effort of nearly two dozen experts on national and state party politics—too many, unfortunately, to cite each of them by name here. Bookended by introductory and concluding chapters written by editors Stacey Hunter Hecht and David Schultz are chapters on each of these ten states by various contributors; there is also a broadly framed chapter on campaigns and voters in swing states, plus one chapter each on two borderline swing states.

To evaluate any study of the swing-state phenomenon, one has to assess, above all, how states were selected for inclusion in this distinctive group. How valid and reliable is the measurement of swing states? The editors lay out three criteria: competitiveness (defined as a vote margin of 5% or less), bellwether status, and incidence of flipping, all during the last seven presidential elections (1988–2012). These are reasonable guideposts, but there is no indication of how frequently a state had to meet each of the three criteria to merit selection as a swing state. In fact, the select list presented in Table X.2 is largely the same (minus two) as an initial one suggested by “the political science literature, media accounts, and campaign activity” (p. xxx). The vaunted swing states of this volume are largely the ones of conventional wisdom. The formal criteria simply help weed out a couple of suspects. The editors are quite frank when they admit, though not too elegantly, that “states that demonstrated more as opposed to less of these criteria became the basis for inclusion as swing states” (p. xxxi).

Spoiling any suspense, here is the chosen list of swing states: Colorado, Florida, Indiana, Iowa, Missouri, Nevada, New Hampshire, New Mexico, North Carolina, Ohio, Virginia, and Wisconsin, hence two more than the 10 alluded to in the subtitle. It would have been less confusing had the subtitle made it a round dozen or if the two add-ons (Indiana and Missouri) had been dropped altogether. Without much doubt, Indiana is a long shot. It qualifies neither as competitive nor as a state that flips often; only once between 1988 and 2012 did it deviate from being a GOP lock. On the face of it, even some of the 10 states that are said to matter do not live up to the swing-state criteria. Take Iowa: The state had a competitive score in just one of the seven elections and voted Republican only once. Or Wisconsin: While a prophetic choice in light of Donald Trump’s upset win there, the state had never flipped in the seven elections since 1988. Taking the volume’s own criteria seriously and requiring that a state would have to meet them, say, at least in three of the seven elections—not an unreasonable requirement—would sharply cut the list of swing states. At the same time, the editors must feel regret over having dropped Pennsylvania, treating this state as safe for Democrats.

Published in 2015 and largely completed the year before, Presidential Swing States nonetheless aspires to tell us something about the then—looming presidential election. If nothing else, we may ask how much these swing states mattered in the 2016 election. As it turns out, the volume is batting below .500 in 2016: Only four of the 10 (or 12) swing states “swung” in 2016: Florida, Iowa, Ohio, and Wisconsin. Moreover, two of them were states with low swing potential; as noted already, Wisconsin had never swung before in the period covered, and Iowa only once. Furthermore, the swing in Iowa as well as Ohio was so wide, exceeding 10 points, as to remove them from the competitive column for 2016. Meanwhile, two states that did not make the cut swung to the Republican side and helped deliver a majority in the Electoral College for Trump: Pennsylvania, which dropped from the editors’ radar, and Michigan, which was never on it. Several other states also put in bids with near-miss swings in 2016: Maine and Minnesota. The point is not to lambast anyone’s predictive performance but to affirm that swing states still remain something akin to the Holy Grail, which is to say highly elusive and still sought.

In all fairness to the editors and contributors, most of the book presents electoral vignettes of the 12 states. Each of those chapters is chock full of information about a given state’s electoral history, survey and exit poll results, campaign activity in presidential elections, and more. Each is also guided by the ultimate question of what made this state a “swing state.” Aside from idiosyncratic circumstances, four broad answers emerge: partisan balance, Independent size, ideological distribution, and demography. The Colorado chapter makes a point with a telling graph (p. 169). It shows Democrats and Republicans in the state electorate, according to party identification, with roughly the same numbers since 2008, and Independents ahead of either of them: the perfect recipe for a competitive state that is poised to swing. North Carolina, on the other hand, dubbed “the bluest red state in America” in this volume, is a state where Democrats still predominate in the electorate, as far as party identification is concerned. The Democratic edge is offset, however, as the chart on page 116 makes clear, by the conservative tilt in the state’s electorate. And with Independents numbering fewer than either partisan group, North Carolina’s swing potential would rate as quite low. Indeed, in the period covered here (1988–2012) the state has swung Democratic only once (for Obama in 2008). One wishes that charts like these for Colorado and North Carolina were included in every state chapter.

One wonders if the 2016 presidential candidates, or their staff at least, read this volume. If Hillary Clinton had done so, she might have caught a warning about one state in particular on the list of swing states. GOP victories in state elections and razor-thin margins in recent presidential contests augured well for a swing in this state in 2016. In 2012, Obama put in several visits, according to the chapter on this state by Neil Kraus and Aaron C. Weinschenk, making it “unlikely that presidential campaigns will ignore the state in future elections” (p. 143). Well, Hillary Clinton did just that—ignore the state and the admonition. She was a no-show there during the general election campaign, while Donald Trump stumped the state in the final stretch of the campaign. It is a bright, shining moment in this volume about swing states that it included Wisconsin.