Castro says he will drop out of 2020 race if he doesn't raise $800K in next 10 days

Former Housing and Urban Development Secretary Julián Castro appealed to supporters on Monday to donate $800,000 by Oct. 31, saying he would be forced to end his presidential campaign otherwise.

Castro tweeted out the call for donations Monday, saying, "This is a critical moment- if my campaign can't raise $800,000 by October 31st, my campaign will be silenced for good.

The tweet included a video lauding Castro for "saying what no one else would," citing his call for decriminalizing crossing the U.S. border and warning "we're in danger of losing Julián's voice."

Sen. Cory Booker (D-N.J.) tried a similar tactic in September, warning that without $1.7 million in donations, "we do not see a legitimate long-term path forward." The appeal was successful, with the Booker campaign raising $1.78 million over the next nine days.

"This moment is a testimony to the power of what's possible when people unite in common purpose and work toward a shared goal," Booker wrote in September.

Castro polls at an average of 0.8 percent in the crowded Democratic field, according to the RealClearPolitics average of presidential primary surveys, but has driven interest with a series of widely-watched moments in the primary debates, including a confrontation with former Vice President Joe Biden at the September debate.