Democrat presidential hopeful and former Housing and Urban Development Secretary Julián Castro chose to fundraise Friday off of an attack on former Vice President Joe Biden during the third round of Democrat debates in Houston, Texas.

“I had a critical choice to make on the debate stage last night,” Castro said in a campaign email to supporters. “I could either play it safe and give Vice President Biden a free pass like everyone else. Or I could speak up, challenge the conversation, and demand answers for you and your family.”

“I’m not in this race to play it safe. This fight — our fight — is too important to me to stay quiet when what I hear doesn’t add up,” Castro continued. “I spent every second on that stage fighting for you — and now I’m being attacked for it.”

Castro then stated his interaction with Biden was the largest “obstacle” he has faced.

“This is now the biggest obstacle I have ever faced,” he added. “Can I count on you to take a stand for me with $5?”

Castro’s encounter with Biden on health care on the debate stage has been widely criticized by Democrats who consider his words an attack on Biden’s age and mental state.

According to Castro, Biden contradicted himself during the debate on the issue of whether people would have to buy into his proposed system related to health care.

“Are you forgetting what you said just two minutes ago?” Castro asked Biden. “I can’t believe that you said just two minutes ago that you had to buy in and now you’re forgetting that.”