An eager reader alerts me to the Secretary of State's announcement minutes ago that Clayton Walker will not be on the November ballot as an Independent candidate for U.S. Senate.

Brookings resident Mary Perpich submitted a challenge to Walker's petitions May 8, specifically questioning the validity of over 1,800 of Walker's 3,429 submitted signatures. With the 52 signatures the Secretary of State's office invalidated in its initial review, Walker had only a 206-signature buffer before falling below the 3,171 needed to get on the ballot. That's less than 12% of the signatures the challenge specifically identified.

Apparently, the Secretary of State found at least 207 additional invalid signatures.*

That means South Dakotans will see a maximum of four possible candidates on their November ballot: Rick Weiland, Gordon Howie, Larry Pressler, and a Republican to be named later.

The SOS announcement doesn't give any details about the challenge, but keep your eyes on the Madville Times as we seek the specifics of what kept Walker out of the race.

*Update 17:13 CDT: David Montgomery reports for that Sioux Falls paper that the actual number of invalidated signatures was 1,613. That means 88% of Perpich's challenged signatures were invalidated. It also means that, in the whole batch of signatures Walker submitted, over 48% were invalidated, either by the SOS Office's initial review or as the result of the challenge.