The Volokh Conspiracy

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Slippery Slope Arguments

Political Momentum Slippery Slopes


[For the last month, I've been serializing my 2003 Harvard Law Review article, The Mechanisms of the Slippery Slope, and I'm finishing it up this week.]

Following the passage of the Brady Bill by the House of Representatives in 1991, the pro-gun-control movement was jubilant, not only savoring its victory but anticipating more to come. "The stranglehold of the NRA on Congress is now broken," said then-Representative Charles Schumer. "[T]hey had this aura of invincibility … and they were beaten." One newspaper editorialized that "with the post-Brady Bill momentum against guns, we hope fees (including on gun makers) can be increased, and the monitoring of dealers tightened," thus "reduc[ing] the total number of weapons in circulation." Decision A (the Brady Bill) was thus seen as potentially leading to a decision B (further gun controls) that may not have been politically feasible before decision A had been made.

Why would people take this view? Say that the gun control groups' next proposal (B) was a handgun registration requirement, and that right before the Brady Bill (A) was enacted, B would have gotten only a minority of the vote in Congress—perhaps because some members were afraid of the NRA's political power, which is to say the power of the voters who are influenced by the NRA. Wouldn't B have still gotten only a minority of the vote even after the Brady Bill was enacted? The conventional explanation for the importance of the NRA's victory or defeat is "political momentum," but that's just a metaphor. What is the mechanism through which this effect might operate (even if it appears in retrospect not to have operated in this particular situation?

The answer has to do with imperfect information. Most legislators don't know the true political costs or benefits of supporting proposal B; they may spend some time and effort estimating these costs and benefits, but their conclusions will still be guesses. And in this environment of limited knowledge, decision A itself provides useful data: the NRA's losing the Brady Bill battle is some evidence that the gun-rights movement may not be that powerful, which may lead some legislators to revise downward their estimates of the movement's political effectiveness. So behind the metaphor of "momentum" lies a heuristic that legislators use to guess a movement's power: a movement that is winning tends to continue to win.

This phenomenon is different from the political power slippery slope, because it focuses on the movement's perceived power in the eyes of legislators, not on its actual power. And it's different from the attitude-altering slippery slope, though both operate as a result of bounded rationality: In an attitude-altering slope, A's enactment leads decisionmakers to infer that A is probably a good policy, and thus that B would be good, too. In a political momentum slippery slope, A's enactment leads decisionmakers to infer that the pro-A movement is probably quite strong, and thus that the movement will likely win on B, too. And since legislators tend to avoid opposing politically powerful movements, they may decide to vote with the movement on B.

Some legislators, of course, will vote their own views, and others may oppose B despite the movement's perceived strength, because they know that their own constituents disagree with the movement. But a movement's apparent strength may affect at least some legislators, and in close cases this may be enough to get B enacted.

Citizens may also change their estimates of a movement's power based on its recent record. Citizens don't care as much as legislators do about backing a winner (though backing winners may make them feel good), but potential activists and contributors tend to prefer to spend their time and money on contested issues rather than on lost causes or sure victories. Likewise, voters may be more likely to choose among candidates based on a single issue when that issue seems up for grabs, rather than when success on that issue seems either certain or impossible.

Thus, when a movement's success in battle A makes the movement seem more powerful and its enemies more vulnerable, and therefore makes the outcome of battle B seem less certain than before, potential activists may be energized. For instance, one history of Prohibition suggests that the 1923 repeal of a New York state prohibition law "gave antiprohibitionists a tremendous psychological lift. The hitherto invincible forces of absolute and strict prohibition"—only four years before, over two-thirds of Congress and three-quarters of state legislatures ratified the Eighteenth Amendment—"had been politically defeated for the first time. Could not other, and perhaps greater, victories be achieved with more determination and effort?"

So it's sometimes rational for voters and legislators to support or oppose decision A based partly on the possibility that A will facilitate B by increasing the perceived strength of the movement that supports both A and B. For example, those who want to see expansion from a modest gun control to broader controls may take the view that, in the words of a 1993 New York Times editorial: "In these early days of the struggle for bullet-free streets, the details of the legislation are less important than the momentum. Voters and legislators need to see that the National Rifle Association and the gun companies are no longer in charge of this critical area of domestic policy." And those who oppose the broader downstream controls might likewise try to prevent this sort of momentum by voting against the modest first steps, even if they would have otherwise supported those steps.

This is especially so because movements rarely just disband after a victory. Successful movements often have paid staff who are enthusiastic about pushing for further action, and unenthusiastic about losing their jobs. The staff have experience at swaying swing voters, an organizational structure, media contacts, volunteers, and contributors. It seems likely that they will choose some new proposal to back. {A movement's victory or defeat in battle A may also affect the movement's internal power structure: if the movement loses, its leaders may be discredited, and others, either more radical or more moderate, may gain control; if the movement wins, those leaders who most strongly supported the winning strategy may gain more power. The result in A might thus affect the movement's willingness to back proposal B and not just its political ability to do so—though such effects may be hard to predict, especially for outsiders who know little about the movement's internal politics.}

This possible slippage seems more likely still if the pro-A movement's leadership is already on the record as supporting the broader proposal B. For instance, many leaders in the gun control movement have publicly supported total handgun bans, even though their groups are today focusing on more modest controls, and some gun control advocates have specifically said that their strategy is to win by incremental steps. Likewise, if a group's proposal is so modest that it seems unlikely to accomplish the group's own stated goals, then we might suspect that a victory on this step will necessarily be followed by broader proposals, which the momentum created by the first step might facilitate. In such cases, foes of B may well be wise to try to block A, rather than wait until the pro-B movement has been strengthened by a success on A.

{Naturally there's a possible cost to this strategy: sometimes, blocking decision A may make B more likely, for instance if it enrages a public that thinks that something needs to be done. This is a common argument for compromise: let's agree on the modest concession A (say, a modest gun control) because otherwise voters might demand B (a total gun ban). The discussion of political momentum slippery slopes merely identifies one possible cost (from the anti-B movement's perspective) of such compromises.}