“An organization called ‘True the Vote,’ which is an offshoot of the Tea Party, is leading a voter suppression campaign in many states,” Boxer wrote in the letter to Perez. “This type of intimidation must stop. I don’t believe this is ‘True the Vote.’ I believe it’s ‘Stop the Vote.’”

The group describes itself as a citizen movement to prevent ballot fraud, though voter fraud is highly uncommon.

In the letter, Boxer cited an interview of a woman in the article who is recovering from cancer and received a letter questioning her residence and right to vote in this election. The woman was confused by the charge since she had lived in that location for seven years.

“The right to vote has been the result of a long and difficult struggle in America,” Boxer wrote. “It has taken generations to ensure full voting rights for minorities, women, and young people. No group can be allowed to intimidate or interfere with this fundamental right that is essential for American democracy.”

Boxer urged an investigation into the group and the alleged voter suppression.

“The Voting Rights Act of 1965 and the National Voter Registration Act of 1993 prohibit persons from knowingly and willfully intimidating or attempting to intimidate, threaten or coerce another person for voting, attempting to vote, or registering to vote,” her letter stated.