He lost to Corbett during the 2004 GOP primary for attorney general.
Recent polls have shown Corbett with lackluster approval ratings. In one August survey, they fell below 30 percent, largely due to his handling of the Jerry Sandusky investigation.
While those numbers have improved slightly in recent months, November losses by the governor's endorsed candidates for attorney general, U.S. Senate, and auditor general have many within his party worrying he is vulnerable to a Democratic challenge.
So far, John Hanger, a former secretary of the Department of Environmental Protection, is the only Democrat to announce he intends to run.
"Corbett is vulnerable, and we Republicans need to be thinking about changing horses," Castor said Wednesday. "We have to select the best candidate in 2014."
Castor said his differences with the governor had less to do with ideology than leadership style.
Despite his party's holding both houses of the legislature, the governor has made little progress on key issues such as pension reform, privatization of the state's liquor sales, and Marcellus Shale, he said.
Despite emerging from his first commissioner run in 2007 as Montgomery County's top vote-getter, he found himself shoved to the sidelines when his running mate James R. Matthews formed a bipartisan alliance with Democrat Joseph Hoeffel III.
The split set off four years of public bickering, catcalling, and caterwauling that led critics to dub the three as "the Bickersons" and that cast Castor as the board's resident contrarian.
Hoeffel retired last year and Matthews left office under indictment for perjury. Since then, Castor has proved a cooperative partner with the county's new Democratic majority led by Chairman Josh Shapiro.
Castor's announcement of a potential run appears timed to coincide with this weekend's Pennsylvania Society dinner in New York City.
The event has traditionally been used as an opportunity for candidates considering statewide runs to drum up support.
Contact Jeremy Roebuck at 267-564-5218 or firstname.lastname@example.org, or follow on Twitter @jeremyrroebuck.