The Iowa Caucuses are coming up on Monday, and for the first time, smartphones will play a role in calculating who wins. But it’s not a government app that party leaders will be using to file totals, it’s a Microsoft product. And that has at least one candidate concerned.

In an interview with MSNBC, Bernie Sanders’ Iowa campaign manager Pete D’Alessandro was suspicious of a large corporation’s intentions in helping total the vote. “You’d have to ask yourself why they’d want to give something like that away for free,” he told the news channel.

And Sanders’ team has built its own, separate reporting system to double-check the results. The campaign is also using a dial-in system to provide even further redundancy in keeping Microsoft’s system honest.

“It’s just a way that our folks can have an app that we trust to get the numbers to us in a timely fashion,” D’Alessandro told MSNBC. “I’m always going to be more for sure on the stuff that my people had control over the entire time… If there are any problems, we can spot them right away.”

Hillary Clinton’s campaign is also using a secondary counting system to double-check totals, but hasn’t publicly stated skepticism about Microsoft’s involvement.

“The Iowa Caucuses provided a unique, non-partisan opportunity to use technology to help evolve the reporting process,” a Microsoft representative said in a statement. “Microsoft is providing technology and services solely to administer and facilitate a neutral, accurate, efficient reporting system for the caucuses. We are proud to partner with the Iowa Democratic and Republican parties to ensure accurate results on caucus night.”

Sam Lau, the communications director for the Iowa Democratic Party, released this statement:

“The Iowa Democratic Party has always believed in the importance of new election technology, and we have been proud to partner with both the Republican Party of Iowa and Microsoft on our new 2016 Iowa Caucuses reporting app that has been in the works for more than a year. Microsoft and their App partner, InterKnowlogy, are global leaders in the technology industry, and we completely trust the integrity of their staff and the app. The app will help make caucus reporting more efficient, accurate and secure, and we look forward to seeing it in action on caucus night.”

The secondary systems are actually common in caucuses, which themselves are downright unusual when compared to standard elections. The caucus process involves literal headcounts, makes party members physically line up in front of a candidate’s representative and is run by the parties themselves instead of the government.

And all that’s sticking around for this primary cycle. The only thing Microsoft is doing is changing the way the caucus totals from each district are collected to determine the overall winner in the state.

This is the first time a smartphone app will be used to calculate caucus totals for a national election. Microsoft developed the app, which it’s offering for free, after the disastrous 2012 Iowa caucus. During those primaries, Mitt Romney claimed victory in Iowa for two weeks until further accounting uncovered Rick Santorum as the real winner.

That error was based on an automated dial-in system that was prone to error. For example, there was no way to check if users dialed in the right totals, so a small typo could cause a huge error.

Microsoft’s solution is a mobile, responsive, cloud-based system that will count the votes instead of a dial-in service. Each party will have a separate application (since, in another strange twist, Democrats and Republicans have slightly different caucus setups), and the parties have both trained with Microsoft to test the app before the big day.

But Sanders’ camp still isn’t clear why Microsoft is a part of the election at all. His team is famously against the idea of corporations getting any more involved in the fabric of American life than they already are, and he’s brought up concerns about Clinton’s ties to big companies before in this election.

Microsoft’s system will still be used Monday, but if things don’t turn out in Sanders’ favor, the software giant could end up at the center of a controversy it was trying to solve.