The United Steelworkers union announced its support Monday of U.S. Rep. Mark Critz, D-Johnstown, in the increasingly competitive race for the new 12th Congressional District.

In congressional matters next door in the 18th District, Democrat Larry Maggi, the chairman of the Washington County commissioners, announced he would get into the race to challenge incumbent U.S. Rep. Tim Murphy, R-Upper St. Clair.

Nominating petitions for statewide races go into circulation this week, so momentum is picking up speed in the run-up to the state's April 24 primary. Republican mapmakers combined the seats of Mr. Critz and fellow Democratic incumbent Jason Altmire of McCandless, forcing them to face off then, so both men have exactly three months to introduce themselves to new constituents.

The endorsement by the Steelworkers union, and its 32,000 active and retired members, should go a long way to help Mr. Critz do that in Mr. Altmire's backyard in suburbs north of Pittsburgh.

"Mark has always been there, not just for the Steelworkers union, but for working families," said union president Leo Gerard at the announcement at union headquarters Downtown.

Not a word was said about Mr. Altmire at the event, as union officials said they hoped to keep the primary campaign from turning negative. "This is a very positive thing for us," said Tim Waters, the USW's political director. Republicans in charge of redistricting "threw them together and would like to see them fighting each other."

The most heated rhetoric came when talking about fighting for manufacturing and working-class jobs.

Mr. Critz was a former aide to the late Pennsylvania Rep. John Murtha, and the candidate said Mr. Murtha taught him that "sometimes you have to throw elbows. You have to stick your neck out. And I haven't been afraid to fight anyone when it comes to the values of working men and women, and our seniors."