HARRISBURG, Pa. (AP) - Allentown Mayor Ed Pawlowski is expected to announce that he's running to challenge U.S. Sen. Pat Toomey's re-election bid, creating the potential for a contested Democratic Party primary in 2016.

Pawlowski planned an announcement Friday.

A political adviser, Mike Fleck, wouldn't say what Pawlowski will announce. But Democratic Party Chairman Jim Burn says Pawlowski has been calling party officials to inform them he has decided to run.

First-term Sen. Pat Toomey, a Republican from suburban Allentown, was elected in 2010. Also running is Democrat Joe Sestak, a former congressman from suburban Philadelphia who narrowly lost to Toomey in 2010.

Pawlowski briefly tested his statewide electoral prospects in last year's governor's race, but dropped out after reporting disappointing fundraising. He has been Allentown's mayor since 2006.