Hillary Clinton's narrow win in the Nevada Democratic caucus was a major blow to the Bernie base. Spencer Thayer, a Chicago-based developer and Sanders supporter, decided to do something about it.

For Democratic voters who don't want to vote for Hillary , Thayer created an outlet. He registered the domain last December but did not begin working on the campaign until Feb. 20, 2016. Within 72 hours, more than 12,000 pledges were submitted — about three every minute. Thayer said:

I think the popularity of the pledge stems from a rejection of the corrupt two-party system … Leftists feel the Democratic Party doesn’t represent their values—and Progressives are sick of being bullied into supporting center-right candidates. Many who’ve signed the pledge say they’ll support Jill Stein and the Green Party. A lot of these individuals feel that supporting a third party has the potential to revive the corpse of American democracy—and that voting their conscience is the only responsible way to go.

The site features a viral video about issues on which Hillary Clinton has flip-flopped over her career. It also displays a list of Clinton's missteps, such as being on the board of Walmart as the company fought unions, and calling some young black men "super-predators."

"I support Bernie because I believe that shifting the narrative of socialism in America helps push, in some small measure, against the cultural hegemony of capitalism," Thayer explained.

"I was initially impressed by Sanders when he was one of the only fierce congressional critics of the 2001 Patriot Act, so when he started contemplating a presidential run in March of 2014 I was already entirely on board."

Many members of the #BernieorBust voters plan to cast a write-in ballot for Sanders, should he not be the nominee. But Thayer's main goal is to make sure they don't stay home on Election Day. "As long as Hillary Clinton is running and as long as the American electorate feels disenfranchised I think people will continue to take the pledge."