<p>PHILADELPHIA (AP) - Moderate Republican Sen. Arlen Specter beat back a tough primary threat Tuesday, barely defeating a conservative congressman who lacked support from party leaders but gained momentum by casting the four-term incumbent as too liberal.</p>
<p>Specter, 74, eked out a win against Rep. Pat Toomey, 42, despite a low turnout among Pennsylvania's 3.1 million registered Republicans that had been expected to aid the challenger.</p>