HARRISBURG, Pa. -- State Treasurer Robert Casey said Friday that he will seek the Democratic nomination for U.S. Senate next year.

Meanwhile, former treasurer Barbara Hafer has dropped out of the race at Gov. Ed Rendell's request.

"The governor asked me to get out and step aside," she said. "He really didn't really tell me why he was supporting Bobby."

Hafer's candidacy plans were raising the possibility of a primary fight that state party leaders feared would wreck any chance of defeating Republican U.S. Sen. Rick Santorum.

Recent polling has indicated that Casey, the son of late Gov. Robert P. Casey, would be the Democrats' best hope for unseating Santorum.

An independent poll in mid-February showed Casey as the only prospective Democratic candidate with an apparent lead over Santorum, 46 percent to 41 percent.