The Town Council in Standish condemned the sign on Thursday in a 6-0 vote and declared it reprehensible at a meeting where some residents defended the store owner, saying he had a right to free speech even if in bad taste, local authorities said.
"The town of Standish condemns in the strongest terms any such alleged activity calling for violence against any individual no matter their position, race or ethnicity," said the resolution posted on the town's website.
The sign in the Oak Hill General Store asked customers to place a $1 bet on the date of Obama's assassination, and said "Let's hope someone wins," the Portland Press Herald reported. It was called the "Osama Obama Shotgun Pool."
The store in the town of 9,285 people in southwest Maine has remained closed since reports of the sign appeared in the media on Sunday.
About 80 people attended the meeting, including some who defended the store owner, said town clerk Mary Chapman.
"There were folks on both sides of the issue," Chapman said in a telephone interview. "People were passionate of their opinion but very respectful of others."
Obama's historic election victory as the nation's first black president has sparked racist incidents nationwide, according to groups that monitor hate crimes.
Obama, an Illinois senator, won the November 4 presidential contest in Maine over Republic Sen. John McCain of Arizona.