It didn't take long for State Sen. Robert C. Wonderling's jump to private-sector work to set off political waves.

Montgomery County Commissioner Bruce L. Castor Jr., whose authority was cut by a power-sharing deal, said yesterday that he was considering a run to fill fellow Republican Wonderling's seat.

"If I got there, I would be in the majority with people who actually wanted to work with me," Castor said.

But he isn't the only Republican with eyes on the post: State Rep. Robert Mensch said yesterday via an e-mailed news release that he was a candidate. However, Mensch did not return a phone call after Castor said he might run, and Mensch also deleted a post at the Web site about running.

The race figures to be a heated partisan battle, with Democrats eager to turn their voter-registration gains in Bucks and Montgomery Counties into a Senate gain, said G. Terry Madonna, a political analyst with Franklin and Marshall College. Wonderling's 24th Senate district includes northern Bucks and Montgomery Counties, along with parts of Lehigh and Berks Counties. Wonderling, who Monday was named president of the Greater Philadelphia Chamber of Commerce, likely will be replaced in the Senate in a fall special election.

"I expect a major battle, probably the most expensive Senate election in state history - with all the stops pulled out," Madonna said in an e-mail. "Control of the Senate is not on the line, but the Republicans need to contain their losses in the suburbs or in a few years run the risk of being in the minority."

Castor said he would decide formally whether he was running within "days or weeks."

If he moved to the Senate, Montgomery County's judges on Common Pleas Court, who are all Republicans, would name Castor's Republican successor.

That could change the tone of county politics, since County Commissioners Chairman James R. Matthews, a Republican, aligned himself with the lone Democrat on the three-member body, Joseph M. Hoeffel III, out of differences with Castor.

Yesterday, Matthews said he believed Castor would have "an excellent chance" of maintaining Republican control of Wonderling's Senate seat.

"That would be very, very good for the party," Matthews said.

Should Castor leave for the Senate, Matthews said, he likely would continue his bipartisan agreement with Hoeffel.

"There's a greater potential for more unanimous votes," Matthews said.