HARRISBURG, Pa. - Gov. Tom Corbett is telling top Pennsylvania Republicans that he supports a Chester County entrepreneur, Steve Welch, to be the party's candidate to challenge Democratic U.S. Sen. Bob Casey, as a GOP endorsement vote nears in the crowded field.

Brian Nutt, a political adviser to Corbett who also works for a firm that is advising Welch's campaign, said Thursday that the governor made his selection after talking to some of the candidates.

Corbett's decision comes less than two weeks before the Republican State Committee meets in Hershey to consider endorsing a candidate in the six-person field vying for the Republican nomination to challenge Casey's bid for a second six-year term.

Chester County GOP Chairman Valentino DiGiorgio said he heard from the governor's staff on Wednesday about Corbett's decision. Party committee members from southeastern Pennsylvania heard the Senate candidates speak at a Valley Forge forum on Wednesday night, but have not settled on a candidate to back, DiGiorgio and others said.

"There's not a great deal of name ID and name recognition for the candidates, so there's still a lot of questions," Delaware County GOP Chairman Andrew J. Reilly said.

The state party's endorsement meeting is Jan. 28; the primary is April 24.

On Thursday, the campaign of rival Tim Burns attacked Welch in an Internet video ad, in part for switching his party registration in 2008 to vote for Barack Obama in the Democratic presidential primary and giving a campaign donation in 2006 to a Democrat, Joe Sestak, who was running for the U.S. House at the time. Welch's campaign has said he voted for Republican John McCain in that year's general election and has switched his registration back to the Republican Party.

Welch and Burns, both entrepreneurs, appear to be the front-runners for the party endorsement, and both have said they probably wouldn't run without it.

Other GOP Senate candidates include former coal industry executive Tom Smith of Armstrong County; former state Rep. Sam Rohrer of Berks County who unsuccessfully challenged Corbett in the 2010 GOP gubernatorial primary; Bucks County manufacturing executive David Christian, who ran unsuccessfully for Congress twice; and lawyer Mark Scaringi of Cumberland County.

Smith's and Rohrer's campaigns say they will remain candidates even if the party endorses someone else. Smith won the northeast central caucus straw poll and has invested $5 million of his own money into his campaign.

Welch, of Malvern, filed paperwork to run for U.S. House in 2010 in two different suburban Philadelphia congressional districts, but he bowed out in deference to party-endorsed candidates. He started a company that makes valves and other components for the biotech industry.

Burns, of Eighty-Four, about 20 miles southwest of Pittsburgh, got his start in business by founding a company that writes prescription software for pharmacies. He later lost two elections in 2010 for the U.S. House seat left vacant by the death of Democratic Rep. John Murtha.

Earlier this month, Burns won a straw poll for Casey's seat in the GOP committee's central Pennsylvania caucus. The southwest and northwest caucuses meet Saturday.

"The reason Tim is in first place in the delegate count is because he's a consistent conservative and a lifelong Republican who can beat Bob Casey," spokesman Ray Zaborney said.