Other birthday cards feature Russian president Vladimir Putin, Vogue editor Anna Wintour, or Venezuelan president Hugo Chavez. Each pokes fun at the president, and is intended to be sent between supporters.

The president, meanwhile, is also planning to use his birthday to political advantage. Obama plans to host a fundraiser and birthday celebration at his Chicago home, only the second time the president has visited his Hyde Park house since winning election. The Obama campaign has been urging supporters in recent weeks to donate for a chance to attend, and asking supporters to sign a virtual birthday card for the president.

On Thursday, the president told a crowd in Florida that he'd like to win their state for his birthday.

"I'm going to be 51 on Saturday. Fifty-one. Michelle says I look 50. That's not bad," Obama said, as the crowd broke into a rendition of "Happy Birthday."

"If I'd known you guys were going to sing, we would have had a cake," Obama said. "And then I would have blown out the candles. I would have made a wish — that probably would have had to do with electoral votes. Winning Florida wouldn't be a bad birthday present."