HARRISBURG — The state’s highest court on Thursday struck Gov. Tom Corbett’s only Republican challenger from the May 20 primary election ballot, leaving Corbett unchallenged for the GOP nomination he was favored to win anyway.

In a 5-2 decision, the state Supreme Court reversed a Commonwealth Court ruling on grounds that conservative activist Bob Guzzardi’s failure to file his statement of financial interests on time with the State Ethics Commission doomed his candidacy.

“The untimely filing of the statement constitutes a fatal defect that precludes a candidate’s appearance on the ballot,” the majority wrote.

Challengers backed by state Republican Party had raised the late ethics commission filing during a two-day hearing, but Commonwealth Court Judge Mary Hannah Leavitt ruled that Guzzardi was not to blame because of mistakes by State Department employees.

Justices Max Baer and Debra McCloskey Todd dissented, saying Guzzardi was “ready, willing and able” to file the statement on time but did not because a State Department employee said it was unnecessary.

Guzzardi, an outspoken critic of Corbett and the state Republican establishment, said Thursday he was surprised that the party “spent so much time and energy to remove a Republican from a Republican ballot.”