The special election to replace the late U.S. Rep. John Murtha’s seat in Congress will be held on May 18, the same day as the state’s primary.

A spokesman for Gov. Ed Rendell said holding the election any other day would have cost the state “well over $600,000.”

The decision to hold it on May 18 was expected nearly universally by observers, and the timing could help the Democratic cotenders because of the party’s competitive U.S. Senate and gubernatorial races.