Washington (CNN) Hillary Clinton wrote a letter to an 8-year-old girl who lost an election for class president, telling the young student that she knows "too well, it's not easy" to run for "a role that's only been sought by boys."

"While I know you may have been disappointed that you did not win President, I am so proud of you for deciding to run in the first place," Clinton wrote in her letter to Martha Kennedy Morales, a third grader at a Maryland private school.

"As I know too well, it's not easy when you stand up and put yourself in contention for a role that's only been sought by boys," Clinton wrote.

The Washington Post was the first to report on the letter, which Clinton spokesman Nick Merrill confirmed to CNN is authentic.

Clinton wrote that she heard about Martha's experience running for class president through her father's posts on Facebook about the election.

Read More