Democratic presidential candidate Julián Castro said on Monday that he will end his campaign if he can’t raise $800,000 before the end of the month.

"If I can’t raise $800,000 in the next 10 days — I will have no choice but to end my race for President," Castro wrote in an email to supporters. “My presidential campaign is in dire need of financial resources to keep going.

Castro, a former mayor of San Antonio who served as secretary of housing and urban development in the second Obama administration, has struggled to poll above 1% and has not yet qualified for the November debate.

Castro raised $3.5 million in July, August and September but only had $672,000 in cash on hand as of Sept. 30.

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. Help us keep up the fight.



DONATE now: https://t.co/CZKqZ7uYHM pic.twitter.com/opXiNoDn3I

— Julián Castro (@JulianCastro) October 21, 2019

In September, the Democratic National Committee released tighter rules for candidates qualifying for the November presidential debate, narrowing the field and putting pressure on Castro and the other Texan in the race, former El Paso congressman Beto O’Rourke.

Speaking on CNN’s “The Situation Room” Monday, O’Rourke said he plans to stay in the race even if he doesn’t qualify for the November debate.

To qualify for the November debate, candidates must meet one of two polling requirements and reach 165,000 unique donors, with 600 unique donors in at least 20 states. Candidates can receive 3% support in at least four qualifying national polls or 5% support in two polls in Iowa, New Hampshire, South Carolina or Nevada. The polls must be released between Sept. 13 and seven days prior to the Nov. 20 debate.

Both Castro and O’Rourke say they have met the donor requirement. Neither candidate has met the polling qualifications for the next debate.