Republican National Committee Chairman Reince Priebus sent a letter to the Clinton Foundation Monday asking the charity to release voluntarily its correspondence with the State Department while Hillary Clinton served as secretary of state.

“In defending her interactions, Secretary Clinton has maintained that while ‘there’s a lot of smoke … there’s no fire,’ or evidence of Clinton Foundation donors receiving special treatment,” Priebus wrote in the letter to Donna Shalala, president of the charity.