So far, 16 of the campaign's 100 large signs - measuring 4 feet by 8 feet - have disappeared, he said, and some have been defaced.
He said one was burned.
"A lot of good people contributed good money to put up those signs," added Philip Baker-Shenk, chairman of the Republican Central Committee.
Kerry signs are being pinched too, according to Democratic Central Committee Chairman Rick Hemphill.
"We just lost two 4-by-8 signs Monday," Hemphill said. "Two of them were up for exactly 24 hours."
One was vandalized at Hemphill's home, he said.
"Somebody walked off Eastern Boulevard, walked into my yard and broke the sign apart," he said. "It was my sign on my personal property.
"It's what happens. It doesn't surprise me; it doesn't shock me. And it doesn't solve anything. I don't like it ... I wish they'd stop."
He attributed the sign sabotage to "misguided people out there who think it makes a difference."
Although he acknowledged that "you're always gonna have petty vandalism," Baker-Shenk said that this year, "it's much more frequent than ever."
He said the 16 large signs had disappeared in the last four weeks.
Republican volunteer Merilee Kerns of Boonsboro said she reported the vandalism and thefts to the Washington County Sheriff's Department.
"Quite frankly, the sheriff's department's take on it has been that in two weeks it will be over," she said.
Sgt. Mark Knight said the sheriff's department had received calls, but there is "no really active investigation and we have no suspects.
"It's not just the Republicans," Knight said. "I have to say, ''tis the season,' because it's a campaign season and Halloween's just around the corner. We will have more than our fair share of vandalism in the next few weeks."
Knight said he was unaware that a sign had been burned, however. Arson was a more serious matter, he said.
Hemphill discounted theories that the disappearing signs were the work of an organized group on either side.
"I would be surprised if it was the same people," he said. "If we were gonna orchestrate taking out signs, they'd all be gone," he joked. "This is a very emotional election. I think it's people reacting on an emotional level."
Boyer said the Republicans "absolutely will keep replacing" the signs, "right up until Election Day."