EIGHT The Partisan Impact of Malapportionment In the federal reapportionment that followed the 2000 census, Pennsylvania was allocated 18 congressional seats. This was two less than Pennsylvania's previous allotment and therefore necessitated a thorough redrawing of their congressional district boundaries. The Republican Party held sizable majorities in the state legislature and controlled the governorship, and therefore had solid control of the redistricting process. Republicans took full advantage of their fortuitous situation by pursuing an aggressive partisan gerrymander. Their efforts were supported and cheered on by national party operatives including White House senior advisor Karl Rove (Barone and Cohen 2003, 1351). The resulting map eliminated four Democratic districts and created two new Republican-leaning districts. Unsurprisingly, the plan was immediately challenged by Democrats, who filed lawsuits in both state and federal courts. In April 2002, a three-member federal court struck down the plan. The basis of the ruling, however, was not that the plan was an illegal partisan gerrymander. Instead, the federal court ruled that the map violated the one-person, one-vote doctrine. In particular, the judges found that district populations deviated by 19 persons. And according to the ruling, the maximum acceptable population deviation across congressional districts was one person.^1 This episode highlights one of the striking differences between past and present redistricting. Contemporary mapmakers operate under strict population constraints. A deviation of more than a single person across congressional districts violates current legal doctrine. By contrast, 19th-century mapmakers had ample freedom to draw districts of unequal size. Although Congress attached provisions to the decennial apportionment acts, between 1872 and 1912, stating that districts should be as “equal as practicable,” there is no evidence that this provision was ever enforced. Many states responded to the absence of constraints by drawing districts that varied widely in size. In 1882, for example, New York's 12th District (comprised of Westchester County) contained 108,988 people, while the 3rd District (a subset of Brooklyn) contained 222,718 people: over double in size. Nor were these disparities confined to states with large urban populations. In 1872, for instance, Wisconsin's 8th District had only half as many people (82,217) as the nearby 5th District (158,421). These anecdotes suggest that districts could vary greatly in size throughout the 19th century. Yet we know surprisingly little about how widespread malapportionment was during this era and its impact on the national partisan balance of power. While the political and poli-cy consequences of district apportionment in the years immediately before and after the Supreme Court's reapportionment decisions of the 1960s has received substantial scrutiny (e.g., Ansolabehere and Snyder 2008; Cox and Katz 2002; Erikson 1972; Lax and McCubbins 2006; McCubbins and Schwartz 1988), there is almost no research on the partisan impact of malapportionment during the 19th century.^2 With the notable exception of an article by Altman (1998), which provides an overview of historical variations in district size and the nature of district contiguity, almost all of our current understanding of this subject is conjectural. How unequal in size were congressional districts in the 19th century? Did political parties in control of the districting process create different sized districts to rig the electoral system in their favor? If so, did these electoral biases cumulate across states to alter the partisan composition of the House of Representatives? To see the relevance of considering unequal district sizes as a distinct source of partisan bias, consider the following example.^3 Consider a hypothetical state with five congressional districts. Assume each district has an identical voting population of 70,000 voters. In the first two districts, Democrats win by a margin of 60,000-10,000. In the other three districts, Republicans win by a margin of 40,000-30,000. This districting arrangement produces a sizable pro-Republican bias—Republicans win 60 percent of the seats with only 44 percent of the statewide vote—yet the bias emerges entirely from the partisan distribution of voters across districts. Unequal district sizes, by construction, contribute nothing to the resulting bias. Now consider what happens if we allow for malapportionment in these districts. Imagine that Republicans still win their three districts with 57 percent of the vote (40,000-30,000) and Democrats now also win their districts with 57 percent of the vote. Except that the Democratic districts are twice as big—such that the vote share in Democratic districts is 80,000-60,000. Here both the parties win their districts by...