Presidential primaries differ from most other U.S. elections in a number of ways – they’re longer, more candidates tend to run, and everyone competes against candidates from the same party – but maybe the biggest difference lies in the rules. In presidential primaries there are numerous and complicated state, national and convention-level rules that have serious implications for the eventual result (if you don’t believe me, just ask Hillary Clinton).

In the current Republican presidential race, an obscure dictate known as Rule 40 has begun to garner significant attention and will likely do so throughout the primary. So here’s a short explanation of what Rule 40 is, why it won’t matter this cycle and how it might even change before the 2016 Republican convention.

What’s Rule 40?

When people refer to this term, they typically mean the current version of Rule 40(b) of “The Rules of the Republican Party,” which stipulates that at the national convention, a candidate must have the support of a majority of delegates from eight different states in order to win the nomination. I won’t get into all of the specifics on how and why the rule was adopted, but its current form came about in 2012 when the Republican National Committee was trying to limit the visibility and power of libertarian-minded Texas Rep. Ron Paul at the convention and thus present a unified front behind Mitt Romney, the presumptive nominee.

It’s easy to see how a requirement like Rule 40 could become an issue in the 2016 race. The GOP field is crowded, talented and reasonably well-funded. So it’s possible that by the time the convention rolls around next summer in Cleveland, no candidate will have the majority of delegates in at least eight states. Or maybe one candidate will have the majority of delegates in more than eight, but the overall delegate leader won’t. These scenarios are extremely unlikely, but if this primary does stretch all the way to the convention, obscure rules start to take on greater importance.

Why Rule 40 Won’t Make a Difference

Republican lawyer Ben Ginsberg and University of Georgia political science lecturer Josh Putnam (who also runs the excellent FHQ blog) emphasized to RealClearPolitics that Rule 40(b) is temporary. In the week before the 2016 convention, the delegates will have multiple opportunities to change it, so no GOP presidential campaign has to worry about getting delegate majorities in at least eight states.

How the Rule Might Change

This will depend on what happens during the primaries. For instance, suppose that Florida Sen. Marco Rubio secures enough delegates to win the nomination (1,237) as well as a majority in 20 different states, while Texas Sen. Ted Cruz is second in the delegate count and holds a majority in 10 states. In that scenario, the convention delegates might make the threshold 15 states, thus disqualifying Cruz and avoiding a convention where a large number of Republicans vote against their nominee. Or imagine a scenario when no candidate has the crossed the 1,237 threshold heading into the convention but each of the leading candidates – say, Rubio, Cruz, New Jersey Gov. Chris Christie and Donald Trump – has a majority of delegates in seven states. Realizing that a floor fight is inevitable, the delegates could decide that the best thing to do is reduce the state minimum to seven, thus managing the fight in a way that gives each of the leading factions a voice and decreases the risk of anyone bolting the party.

These scenarios are not meant to be predictive or even realistic – they just illustrate some of the ways the convention delegates might respond to different primary outcomes. The bottom line is that Rule 40 is highly unlikely to stand between the leading GOP candidate and the nomination.

This article was updated on Dec. 15 at 4:54 p.m. Eastern time.