Although New Mexicans cast their vote on Super Tuesday, the race was not called until 10 days later. The contest between Sens. Hillary Clinton (D-N.Y.) and Barack Obama (D-Ill.) was painfully close, and there were an astonishing 17,000 provisional ballots cast that had to be counted by hand—about 12 percent of the total number of votes cast. Provisional ballots are given to voters who, for whatever reason, do not appear on the voter registration list but believe they are eligible registered voters, and are counted only after the polls are closed.

There might have been many reasons so many voters had to vote by provisional ballot rather than a regular ballot in New Mexico. Whatever the reason, however, there is no question that New Mexico or another swing state could find itself in a similar predicament come November: a close race in which the presidency will all come down to the counting of provisional ballots. What happened in New Mexico on Super Tuesday should serve as fair warning to all the states that they better know how they are going to handle such a problem should they be confronted with it. And it’s clear that most states do not.

State laws are incredibly vague and incomplete with regard to casting and counting provisional ballots. For example, most states require local officials to ascertain that a provisional voter is in fact “registered” in order for the provisional ballot to count. But few states specify either exactly what qualifies as being “registered” or the specific steps that local officials must take to make this determination.

There are circumstances that routinely arise during the registration process that lead to a voter having to cast a provisional ballot that most states have no policy on. States do not specify whether an individual is “registered” if the Department of Motor Vehicles fails to deliver the registration form to elections administrators. States do not have protocols for what to do if it turns out the Postal Service or a third-party group failed to deliver a voter’s registration form in a timely fashion. What if the voter omits certain required information from the form and it was rejected by elections administrators for that reason? Will that voter’s provisional ballot count?

Likewise, for the most part, state laws do not spell out the steps election officials must take in their investigation into the legitimacy of a provisional ballot. For example, must the local officials contact the Department of Motor Vehicles to look for registration forms that may remain undelivered? Should local officials search their own records for original registration forms, rather than relying solely on information contained in the state’s centralized voter registration database?

Even worse, in some states the provisional voting process operates very differently in different localities within the state. In Ohio in 2006, percentages of provisional ballots that were both cast and counted varied wildly regardless of demographics, a strong indication that different county boards were applying their own rules in the face of insufficiently specific directives from the state. States must have basic, uniform rules in place on these matters to prevent different counties within the states from applying their own rules and thereby opening the state up to voting rights lawsuits based on equal protection.

Ultimately, it may require congressional action to ensure the kind of uniformity necessary to protect the equality of the vote. Since that is not likely before November, the two political parties should take a cue from that state in trouble, New Mexico. Soon after it became clear that the winner of the contest would be determined by the provisional ballots, the Clinton and Obama campaigns came together to devise a mutually agreed upon set of rules for determining what types of provisional ballots would be counted and which would not. Well ahead of the November election, it would benefit the country if the lawyers of the Republican and Democratic parties were able to hammer out a similarly mutually agreed-upon treaty.

Provisional ballots were mandated by federal law in order to ensure that no voter would be turned away without voting when he showed up at the polls. Beyond that, the law said little about whether those voters should have their ballots count. As November approaches, it is up to the states and the parties to act immediately to ensure that a close election does not once again end up in chaos and litigation.

Edward Foley is a professor at The Ohio State University Moritz College of Law and director of the program Election Law at Moritz. Tova Andrea Wang is a democracy fellow at The Century Foundation and was executive director of its Post-2004 Election Reform Working Group comprised of leading law scholars. This article was first published in The Hill.