Montgomery County Commissioner Bruce L. Castor Jr. declined Tuesday to challenge Gov. Corbett in the 2014 Republican primary, citing the difficulty of such a "massive undertaking" given his other obligations.

His decision came after months of seeking to translate grumbling about the governor's performance from some GOP activists into support for an insurgent candidacy. It removes one potential headache for Corbett, whose anemic approval ratings in recent polls have Democrats lining up to run against him.

"Simply put, my duties as Montgomery County commissioner, a lawyer with Elliott Greenleaf, and the responsibilities to my family make a massive undertaking such as running for governor impossible for me this election cycle," Castor said in a statement posted Tuesday afternoon to his Facebook page.

Since fall, Castor has been criticizing Corbett as a weak leader who has not done enough to advance conservative causes such as legislation aimed at weakening unions.

Recently, Castor expressed concern that the governor might reverse his decision to turn down millions in federal money to expand the Medicaid program of health care for the poor. Activists on the right believe that accepting the money, a part of the Obamacare law, would leave state taxpayers on the hook later.

Castor said last month that it had been difficult to scare up support for a challenge to the incumbent.

"It's disappointing that so many people in the Republican Party are invested in the governor that they are unwilling to face the signs that we're in deep trouble next fall," Castor said Tuesday. "People were unwilling to even consider an alternative."

Castor was Montgomery County district attorney from 2000 to 2008, when he began his first term as commissioner. He had challenged incumbent Tom Ellis, a former ally, in the 2007 primary. Castor was reelected in 2011, when Democrats took control of the three-person Board of Commissioners for the first time in the county's history.

In 2004, Castor ran against Corbett for the nomination for state attorney general despite Corbett's having the GOP endorsement. Castor accused party leaders of making a deal with National Committeeman Bob Asher, a Montgomery County power broker with whom he had been feuding. Castor made an issue of Corbett's ties with Asher, who had been convicted in a 1986 pay-to-play case. Corbett won the primary by 53 percent to 47 percent, though Castor carried the Southeastern Pennsylvania counties.