Some candidates lose because they are out-organized, others because they are out-funded. Rick Santorum may have lost because his campaign just wasn’t good enough at paperwork.

Santorum, who finally threw in the towel Tuesday, failed to take advantage of a number of critical opportunities, particularly Michigan in February and Ohio on Super Tuesday. But the real missed opportunity for the former Pennsylvania senator wasn’t in a tight Rust Belt primary—it was before the race even began. In Ohio and Illinois, not to mention the upcoming primaries in Pennsylvania and West Virginia, he did not file full slates of delegates, leaving at least 10 delegates on the table in Ohio and Illinois combined. If his campaign had gone through Pennsylvania and beyond, his filing failures would have continued to cost him.

The 10 delegates Santorum missed out on were relatively meaningless in the big picture. Although winning them would have made the delegate math slightly closer, their real impact was to change the narrative prior to these primaries. Instead of homing in a social conservative-versus-moderate narrative, the national media covered Santorum’s delegate woes, and Mitt Romney’s campaign did not hesitate to emphasize them.

The delegate failures undermined Santorum’s efforts to depict himself as a David fighting Romney’s comparatively well-funded Goliath. Instead of looking like an underdog, his campaign looked like a Mickey Mouse operation.

Santorum always faced the obstacle of having to establish credibility. He lost his last campaign in Pennsylvania by a landslide and was an asterisk in national polling until the eve of the Iowa caucuses, where he famously campaigned “in a truck with a guy named Chuck,” riding shotgun in a pickup from pizza parlor to pizza parlor in rural Iowa. But in the process of trying to scrape his way into relevancy, he hadn’t prepared for what he called “a miracle campaign” in the speech he delivered announcing the end of his presidential bid. The problem with his campaign, as Obama delegate counter Jeff Berman pointed out to The Daily Beast: “What’s the point of a longshot candidacy if you’re not prepared when you catch fire?”

These were not the Santorum campaign’s only ballot woes. He did not qualify for the ballot in Virginia—where only Romney and Ron Paul met the commonwealth’s stringent regulations for its Super Tuesday contest—or in Washington, D.C.’s winner-take-all primary. This particularly hurt him in Virginia, as it left Romney a virtul shoo-in to sweep the state and the former Massachusetts governor was virtually assured an overall Super Tuesday delegate win before the first vote was cast.

Santorum’s failure to make the ballot in Virginia was no surprise. It was known that only Paul and Romney would be on the ballot before the Iowa caucuses. But Santorum’s failure to file for the necessary delegates in states where he was on the ballot made headlines.

Before critical primaries in Ohio and Illinois, the national media would slowly realize that Santorum had fallen short of attaining delegates in several congressional districts, and this theme was already emerging in Pennsylvania. The result lent a “Keystone Kops” air to Santorum’s campaign and undermined his otherwise credible arguments about the shakiness of the conventional wisdom about the delegate count.

If Santorum had managed to file all his delegates, it might not have been enough to carry him to the GOP nomination. But it would have been a significant boost. If his campaign had been able to spend all of its time pushing out its message prior to Super Tuesday, rather than defending its competence, that might have been enough to carry Santorum over the top in Ohio. After all, he only lost the state by 10,000 votes A win there would have changed the race's momentum. But just as Richard III may have lost Bosworth Field for want of a nail, Santorum may have lost the presidency for want of a full delegate slate in Ohio.