HARRISBURG (AP) – Nominating petitions of Gov. Tom Corbett’s only opponent are being challenged. The challenge of Bob Guzzardi’s petitions was filed by four Republican voters who had help from the state GOP. Guzzardi, a conservative Ardmore businessman, needed to collect 2,000 signatures including 100 in each of 10 counties. He turned in over 3,100 signatures, but the challengers say defects in his petitions, such as the signatures of people not registered to vote, left him with the required number of signatures in only eight counties. Guzzardi says the challenges reflect party leaders’ concern that he poses a threat to Corbett’s re-election. He will defend his petitions in court.