Bolivia dismissed its October elections as fraudulent. Our research found no reason to suspect fraud.

By John Curiel, research scientist with MIT’s Election Data and Science Lab. He earned his PhD in political science from the University of North Carolina at Chapel Hill and Jack R. Williams ia researcher with MIT’s Election Data and Science Lab @ WashingtonPost.com, Feb. 27

Bolivians will hold a new election in May — without ousted president Evo Morales

As Bolivia gears up for a do-over election on May 3, the country remains in unrest following the Nov. 10 military-backed coup against incumbent President Evo Morales.

A quick recap: Morales claimed victory in October’s election, but the opposition protested about what it called electoral fraud. A Nov. 10 report from the Organization of American States (OAS) noted election irregularities, which “leads the technical audit team to question the integrity of the results of the election on October 20.” Police then joined the protests and Morales sought asylum in Mexico.

The military-installed government charged Morales with sedition and terrorism. A European Union monitoring report noted that some 40 former electoral officials have been arrested and face criminal charges of sedition and subversion, and 35 people have died in the post-electoral conflict. The highest-polling presidential candidate, a member of Morales’s Movimiento al Socialismo (MAS-IPSP) party, has received a summons from prosecutors for undisclosed crimes, a move some analysts suspect was aimed to keep him off the ballot.

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 [....]

and they go on at length explaining why