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Viewers trying to view the first Democratic debate Tuesday evening complained the CNN mobile app crashed. Reuters

CNN promised to offer free live streaming through its mobile app, but the platform was reportedly off to a rocky start Tuesday evening as the first Democratic debate kicked off in Las Vegas. Viewers flocked to Twitter to complain that the app was down. "Don't say you'll stream the debate if the app goes down every five minutes," one user tweeted.

Network officials had offered the mobile platform free of charge to introduce users to the service. “We are offering this as a preview. To me, there's a longer play here, which is that we want our audiences to know this is a service they can get from CNN going forward. We want to build that user behavior," said Andrew Morse, head of U.S. editorial operations and worldwide digital at CNN, told Mashable before the second GOP debate, which the network hosted.

Fortunately, alternative streaming services were available. The debate was also offered online on CNN.com's home page, on the CNN Politics live blog. Viewers could also watch the Democratic candidates face off on the television stations CNN, CNN International and CNN en Español. Westwood One News was airing the debate live through their broadcast radio stations.

Fox News also faced issues with its live stream of the first GOP debate in August. Users struggled to log in on mobile and web streams of the debate, and were greeted with errors or pages that never loaded correctly.

Tuesday's debate was hosted by CNN and Facebook at 8:30 p.m. EDT at the Wynn Las Vegas. CNN anchor Anderson Cooper served as moderator of the debate, along with Dana Bash, CNN's chief political correspondent, and CNN en Español anchor Juan Carlos Lopez.

CNN anchor Don Lemon also was expected to ask questions, which were compiled from social media. Viewers were given the opportunity to submit questions to the candidate on Facebook and Instagram.

Former Secretary of State Hillary Clinton was positioned at the center Tuesday since she dominates the polls with a 19-point lead. She appeared on stage with Vermont Sen. Bernie Sanders, former Maryland Gov. Martin O'Malley, former Virginia Sen. Jim Webb and former Rhode Island Gov. Lincoln Chafee.

In the latest CBS poll, Clinton is supported by 46 percent of Democratic primary voters. Sanders falls in second place in the Democratic race with 27 percent of the vote.