The media has largely reported the allegations of fraud as fact. And many commentators have justified the coup as a response to electoral fraud by MAS-IPSP. However, as specialists in election integrity, we find that the statistical evidence does not support the claim of fraud in Bolivia’s October election.

The OAS claimed that election fraud had happened

The primary support for claims of fraud was the OAS report. The organization’s auditors claimed to have found evidence of fraud following a halt in the preliminary count — the nonbinding election-night results meant to track progress before the official count.

The Bolivian constitution requires that a candidate either earn an outright electoral majority or 40 percent of the votes, with at least a 10-percentage-point lead. Otherwise, a runoff election will take place. The preliminary count halted with 84 percent of the vote counted, when Morales had a 7.87 percentage-point lead. Though the halt was consistent with election officials’ earlier promise to count at least 80 percent of the preliminary vote on election night and continue through the official count, the OAS quickly expressed concern over the stop. When the preliminary count resumed, Morales’s margin was above the 10-percentage-point threshold.

The OAS claimed that halting the preliminary count resulted in a “highly unlikely” trend in the margin in favor of MAS-IPSP when the count resumed. The OAS reported “deep concern and surprise at the drastic and hard-to-explain change in the trend of the preliminary results.” Adopting a novel approach to fraud analysis, the OAS claimed that high deviations in data reported before and after the cutoff would indicate potential evidence of fraud.

But the statistical analysis behind this claim is problematic

The OAS report is in part based on forensic evidence that OAS analysts say points to irregularities, which includes allegations of forged signatures and alteration of tally sheets, a deficient chain of custody, and a halt in the preliminary vote count. Crucially, the OAS claimed in reference to the halt in the preliminary vote count that “an irregularity on that scale is a determining factor in the outcome​” in favor of Morales, which acted as the primary quantitative evidence to their allegations of “clear manipulation of the TREP system … which affected the results of both that system and the final count.”

We do not evaluate whether these irregularities point to deliberate interference — or reflect the problems of an underfunded system with poorly trained election officials. Instead, we comment on the statistical evidence.