The OC Weekly obtained the email with the controversial photo, which shows the president's face pasted onto the head of a baby chimp.
The caption beneath the picture read, "Now you know why no birth certificate."
Marilyn Davenport, who is a member of the central committee of the Republican Party of Orange County, sent the email.
She told the OC Weekly it was a joke.
"You're not going to make a big deal about this, are you?" Davenport reportedly asked when the newspaper's political blogger reached her for comment. "Oh, come on!"
The RPOC chairman is calling for an ethics investigation and says Davenport should consider stepping down.
City News Service contributed to this report.