(The Center Square) – Recent polling averages show the gap closing in Pennsylvania’s U.S. Senate race. Republican challenger Dave McCormick trails incumbent Democratic Sen. Bob Casey Jr. by 2.6 points, according to RealClear Politics. In five polls conducted between Aug. 8 and Aug. 30, Casey saw his 5-point lead vanish during the week of the Democratic National Convention. In two subsequent surveys, he held McCormick off between 1 and 4 percentage points. A more extensive list compiled by RealClear shows the incumbent senator commanding a double-digit lead during the last week of July. He’s ye…