HARRISBURG — A state judge has ruled that a Republican gubernatorial candidate can stay on the May 20 primary ballot as the lone challenger to Gov. Tom Corbett.

Commonwealth Court Judge Mary Hannah Leavitt ruled today for conservative activist Bob Guzzardi, an Ardmore businessman.

Hannah presided over a two-day hearing on a petition challenge backed by the state Republican Party.

She concluded that challengers to Guzzardi’s candidacy didn’t produce the evidence needed to keep him off the primary ballot.

Guzzardi is an outspoken Corbett critic who’s said he’s running to give party conservatives an alternative.

Corbett campaign spokesman Mike Barley says the governor is focused on running his own campaign.