On February 27, Wisconsin Governor Scott Walker said he won’t challenge the validity of the recall petition filed to remove him from office. See this story. In Wisconsin, signatures are valid if the voter is eligible to register to vote. There is no master list to check the validity of signatures. The only signatures that the Governor might have been able to invalidate would have been duplicate signatures, and names on the petition in which the so-called signer doesn’t exist, or doesn’t live at the address listed on the petition. Thanks to Rick Hasen for the link.