HARRISBURG — U.S. Rep. Jim Gerlach abandoned his campaign for the Republican nomination for Pennsylvania governor Thursday, saying the cost of a statewide campaign is prohibitive.

The withdrawal of the fourth-term congressman from southeastern Pennsylvania leaves only state Attorney General Tom Corbett, who is widely regarded as the front-runner, and state Rep. Sam Rohrer in the race to be decided in the May 18 primary.

Gerlach's announcement, reported by The Morning Call in Allentown, comes barely a month before the Republican State Committee gathers in Harrisburg on Feb. 13 to award its endorsement.

Gerlach said his campaign had raised more than $1 million, but he believes he would need four times that much to be competitive in the primary.

While stopping short of saying he would run for re-election to Congress, Gerlach said he remains passionate about good government and vowed to "continue to raise my voice and work hard in the months and years ahead."

Corbett's candidacy has been bolstered by his office's ongoing legislative corruption investigation. So far, the 3-year-old probe has resulted in 25 arrests of people connected to the House of Representatives, guilty pleas by seven House Democratic staffers and the acquittal of one former Democratic legislator.

A December poll by Connecticut-based Quinnipiac University showed half of Pennsylvania voters are familiar with Corbett, and 80 percent did not know enough about Gerlach to form an opinion about him.

Democrats running in the primary are: Scranton Mayor Chris Doherty, Montgomery County Commissioner Joe Hoeffel, Philadelphia businessman Tom Knox, Allegheny County Executive Dan Onorato and state Auditor General Jack Wagner.