Say you care little about the .50-caliber rifle ban, but your neighbor strongly supports or opposes it. His vote in the election, he says, will be influenced by the candidates’ views on the ban, and he has donated time and money to pro- or anti-ban groups.
If you don’t think the law will tend to lead to broader laws, you might think this fellow is a bit extremist. Some people might enjoy being perceived as rigid on such matters: “Extremism in the defense of liberty,” they might say, echoing Barry Goldwater, “is no vice.” But people who like to see themselves and to be seen by others as “moderate” might not want such a reputation, and might therefore adopt a small change tolerance heuristic. And this may apply to legislators as well as voters—though some legislators cultivate a reputation for never budging on some issues, others might want to avoid looking like “rigid ideologues” to their constituents, or alienating colleagues with whom they’ll have to work again.
Small change tolerance slippery slopes can therefore happen when a law’s opponents don’t want to seem extremist but the law’s supporters don’t mind appearing this way, either because they’re extremist by temperament or because the status quo looks so bad to them that they feel a strong “don’t just stand there, do something” effect. Supporters will push for small changes, and opponents won’t push back much. Of course, if a law’s supporters don’t want to insistently press their case, but the law’s opponents don’t mind seeming insistent, the law will more easily be blocked, and the slippery slope likely won’t happen. The small change tolerance slippery slope, like the other slippery slopes, happens under particular political circumstances; it is a plausible phenomenon, but far from a certain one.
Small change tolerance slippery slopes can also interact with other slippery slopes, for instance when step A ends up being easily evaded and then a small extension B is promoted as a “loophole-closing measure.” The combination of some people’s opposition to situations where a law is being evaded (an enforcement need slippery slope), A‘s enactment changing others’ minds about B‘s merits (an attitude-altering slippery slope), and the tendency of still others not to care much about small loophole-closing proposals (a small change tolerance slippery slope) can facilitate decision B once A is enacted, even if B would have been rejected at the outset had it been initially proposed instead of A.
Finally, small change tolerance can also be reinforced by the need to compromise. Legislators and appellate judges often have to give up something on one issue to get what they want on another, and such compromise is naturally more common on small matters than on big ones. Few judges will explicitly offer to change their votes on one case in exchange for a colleague’s vote on another, but judges routinely compromise on an opinion’s wording (either when an authoring judge changes the wording or when another judge doesn’t insist on a change) to persuade another judge to join, to increase the chances of the authoring judge changing the opinion on another point, or to earn the authoring judge’s goodwill on a future case. Decisionmakers might thus be more willing to compromise on a small step A, then small extension B, and then small extension C than they would have been had the larger extension C been proposed up front.