Former Pennsylvania Gov. Tom Ridge said Thursday that he will not seek the 2010 Republican nomination for the Senate seat held by Arlen Specter, the five-term incumbent who switched last week from the GOP to the Democrats.

Ridge — the state’s chief executive from 1995 to 2001 and the founding secretary of the federal Department of Homeland Security — said in a statement that he decided against a Senate bid “after careful consideration and many conversations with friends and family and the leadership of my party.”

“I am enormously grateful for the confidence my party expressed in me, the encouragement and kindness of my fellow citizens in Pennsylvania and the valuable counsel I received from so many of my party colleagues,” Ridge said. “The 2010 race has significant implications for my party, and that required thoughtful reflection. All of the above made my decision a difficult and deeply personal conclusion to reach.”