The primary battle between challenger Joe Sestak and incumbent Arlen Specter for the Democratic U.S. Senate nomination is tied at 43 percent, according to the Muhlenberg College/Morning Call tracking poll released Friday.

Specter had led 45 percent to 40 percent just a day earlier, although the plethora of polls released in the last week have all shown the 7th District congressman closing fast on what had been a double-digit gap.

The poll surveys 400 likely Democratic voters and has a margin of error of 5 points. Muhlenberg is releasing a new poll on the race until May 16, two days before the primary.