U.S. Rep. Kyrsten Sinema has been under fire from Republicans recently for accepting donations from former Backpage.com founders Michael Lacey and Jim Larkin.

Sinema has since apologized for accepting the donations and said that she wasn’t aware they were associated with the website, which has been accused of facilitating sex trafficking. She donated the money to the Arizona Coalition to End Sexual and Domestic Violence but the Arizona Republican Party is keeping up the pressure on Sinema about the donations.

But just how much do most politicians really know about where their campaign donations come from? For more on this, I spoke with Sheila Krumholz, executive director for the Center for Responsive Politics, which runs Open Secrets, the website that tracks political spending.