JEFFERSON CITY, Mo. (CNN) -- Secretary of State Robin Carnahan walked into the main election office in St. Louis last Friday to cast her absentee ballot and was taken aback when a poll worker asked her to show photo identification.

"I presented my voter registration card, the one you get in the mail with your name, address and polling location, and was asked by a lady -- who was very nice -- for a photo ID. I said, 'Why are

Carnahan, the state's top elections official, told CNN Tuesday she tried to explain to the poll worker that a photo ID is not necessary to vote in Missouri -- the state's Supreme Court struck down the requirement on Oct. 16 -- but was asked two more times for such identification.

"She didn't know who I was, but when she saw my last name, she asked, 'Are you Russ' sister?' referring to my brother who is a congressman," said Carnahan.

Democrat Russ Carnahan represents the state's Third Congressional District.

The poll worker checked with her on-site supervisor and reported back to Carnahan that indeed photo identification would not be necessary to cast a ballot.