PHILADELPHIA (Reuters) - Moderate Republican Sen. Arlen Specter scored a narrow primary win over a conservative congressman on Tuesday in a race that could influence the November battles for control of the Senate and White House. Specter, a four-term Senate veteran and one of the chamber's last moderate Republicans, outlasted Rep. Pat Toomey, 51-49 percent, winning by about 15,000 votes out of more than one million ballots cast. "It's been a very, very difficult campaign," Specter told supporters in a downtown Philadelphia ballroom before the final results were tallied, lamenting the criticism he has faced for his support for abortion...