HARRISBURG, Pa. - The lone Republican running against Gov. Tom Corbett in next month's primary election won a court decision Tuesday that lets him stay on the ballot.

Commonwealth Court Judge Mary Hannah Leavitt's decision in favor of conservative activist Bob Guzzardi, an Ardmore businessman, followed a two-day hearing on a petition challenge backed by the state Republican Party.

Leavitt concluded that challengers to Guzzardi's candidacy did not produce the evidence needed to keep him off the May 20 primary ballot.

In her 34-page opinion, Leavitt turned down three legal challenges to Guzzardi's candidacy.

She ruled that Guzzardi had met the requirement for petition signatures, accurately represented his occupation on his nomination petition and was not to blame for failing to file paperwork with the State Ethics Commission by a March 11 deadline.

The paperwork, Guzzardi's statement of financial interest, was properly filed on March 10 with the Department of State. Leavitt ruled that mistakes by Department of State employees misled Guzzardi and campaign aides about a requirement that they also file the paperwork with the State Ethics Commission. He later filed the paperwork there.

Guzzardi is an outspoken Corbett critic who has said he is running to give conservatives an alternative.

His lawyer, Gretchen Coles Sterns, said she hoped the petition challengers would not appeal further, to the state Supreme Court.

"I would hope that the Pennsylvania GOP would honor Judge Leavitt's ruling and embrace the spirit of competition which has always made America greater," Sterns said.

Corbett campaign spokesman Mike Barley responded to the decision by saying the governor is focused on running his own campaign and noting that he has been endorsed by the state party and by elected Republicans.

The Republican State Committee pulled out all the stops to shield Corbett, whose low popularity ratings underscore his vulnerability, from a primary fight. Its general counsel, Lawrence Tabas, personally questioned witnesses and made closing arguments at the hearing. A telephone message seeking comment from Tabas was not immediately returned Tuesday.

Guzzardi has attacked Corbett for violating his 2010 campaign pledge not to raise taxes by increasing taxes on gasoline and by authorizing new fees on natural-gas drilling.

In an interview last month, he said he envisioned running a low-budget, self-financed campaign that would advocate "less debt, lower taxes, more for taxpayers, less for the government."

Four Democrats are seeking their party's nomination to run for governor in the Nov. 4 general election.