Conservative poster boy Rick Santorum fell to mild-mannered challenger Bob Casey Jr. yesterday, ousted by voters fed up with President Bush and the war in Iraq.

With 81 percent of precincts reporting, Casey held 60 percent of the vote and Santorum 40 percent. Santorum called Casey to concede about 9:30 p.m.

"This was just a little too steep of a mountain to climb," Santorum, 48, told supporters in Pittsburgh last night, surrounded by his tearful wife and six children. "Thank you for believing in a cause that will not end with tonight."

Casey, 46, who sailed to victory as part of the massive Democratic tide that booted GOP incumbents around the country, addressed a jubilant Scranton crowd.