WASHINGTON – Julián Castro is giving his supporters 10 days to help him raise $800,000 or he will have to call it quits for his Democratic presidential bid.

Castro, the former Housing and Urban Development Secretary under President Barack Obama, asked supporters in an email Monday morning help him reach his donation goal by Oct. 31.

"I'm asking you to fight for me like never before," Castro said in the email. "If I don't meet this deadline, I won't have the resources to keep my campaign running. I'm counting on your $5 in this critical moment."

"This isn't a fundraising gimmick — it's the transparency and honesty I have promised you since I entered this race," he continued. "The truth is, for our campaign, these debates have offered our only guaranteed opportunity to share my vision with the American people. If I can't make the next debate stage, we cannot sustain a campaign that can make it to Iowa in February."

Castro has struggled to make waves in a crowded Democratic field.

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He currently stands at 0.8%, according to an average of polling from Real Clear Politics. He also still needs four polls to qualify for the November debate. Candidates need to meet at least 3% nationally or 5% in early state in four polls. Castro hasn't met any of the polling requirements.

However, his campaign has secured the 165,000 grassroots contributions that he needs to make it to November's debate.

Eight candidates have so far qualified for the November debate stage: former Vice President Joe Biden, Sen. Elizabeth Warren, Sen. Bernie Sanders, Sen. Kamala Harris, Sen. Cory Booker, South Bend, Indiana, mayor Pete Buttigieg, entrepreneur Andrew Yang and businessman Tom Steyer.

Castro's tactic comes a couple of weeks after Booker also made a plea to his supporters to help him raise $1.7 million, a goal he met.

Castro's campaign manager Maya Rupert said in a statement that the campaign does not see a path to victory if Castro doesn't make it to the November debate stage.

"Our campaign is facing its biggest challenge yet," she said in a statement. "Secretary Castro has run a historic campaign that has changed the nature of the 2020 election and pushed the Democratic party on a number of big ideas. Unfortunately, we do not see a path to victory that doesn't include making the November debate stage—and without a significant uptick in our fundraising, we cannot make that debate."

Castro also wrote in a tweet Monday morning that his "campaign will be silenced for good" if he doesn't reach this fundraising goal.

"I’m extremely proud of the historic and bold campaign we have built together. But this is a critical moment— if my campaign can’t raise $800,000 by October 31st, my campaign will be silenced for good," he wrote in a tweet. "Help us keep up the fight."