Signatures a high hurdle in Mass. US Senate race Associated Press Copyright 2013 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. Updated 1:46 pm, Friday, February 15, 2013 BOSTON (AP) — For candidates running in Massachusetts' upcoming U.S. Senate special election, collecting the required 10,000 certified voter signatures is a first and daunting challenge. Another potential GOP candidate U.S. Attorney Michael Sullivan is relying on volunteers.