Spokesman Nu Wexler said the 14-term congressman from York left a message for Mulvaney, but had not been able to speak with him directly.
Spratt, 68, had refused to concede defeat late Tuesday, saying he would continue to press for a full accounting of votes in South Carolina's 5th District. Mulvaney, 43, won with 55 percent of the vote to Spratt's 45 percent.
The district along the border with North Carolina has backed a Republican president since Spratt was elected in 1982. Tuesday's results showed voters were no longer willing to split their tickets to keep the moderate Southern Democrat in office.
"Spratt's just been in there too long," said Mike Hemlepp, 75, after casting his ballot in Clover, just north of Spratt's hometown.