The software, which a Clinton precinct captain in Iowa Falls, Jim Lehtola, showed BuzzFeed News on his iPhone, allows them to enter the complete number of attendees at a given caucus, and then to divvy them up by candidate. The app shows how many supporters each candidate needs to reach their thresholds. Precinct captains can then calculate easily whether, say, Clinton can — without cost to her own delegate count — boost O’Malley to a viability. And they’ve been trained, Lehtola said, in that maneuver.

A senior Sanders caucus strategist, who also spoke on background, allowed that caucus rules allow for these kind of math games, but said the Sanders campaign has no similar plan. They have trained their volunteers to play it straight, the strategist said — try to get as many people to the caucus site as possible, and then try to recruit caucus goers from among the candidates not deemed to be viable.

A spokesperson reacted much more strongly.

“It’s sad and telling that their campaign doesn’t think they can win without these kinds of tactics,” said Rania Batrice, Sanders’s Iowa spokesperson. “At the end of the day though, we believe in the caucus process and know it’s in the very capable hands of Iowans.”