James Carville, a strategist for former President Bill Clinton and advisor to his wife Hillary's 2008 presidential campaign, hinted Democrat supporters could be angry if Mr Obama lost, given his lead in the polls.
"If Obama goes in and he has a consistent five-point lead and loses the election, it would be very, very, very dramatic out there," he told CNN.
James Tate, of Detroit's police department, which dealt with violent celebrations after the Detroit Tigers won the baseball World Series in 1984, told congressional newspaper The Hill that problems could flare whichever candidate wins.
"Either party will make history and we want to prepare for celebrations that will be on a larger scale than for our sports teams," he said. "The worst-case scenario could be a situation that requires law enforcement."
In Chicago, where Mr Obama will hold a rally on November 4, the police department has been meeting to discuss security plans for the night. Law enforcement departments in Philadelphia and Cincinnati are also making preparations in case of problems.
Commentators point to the surge in voter registration and large turnout in the primaries as reasons why there could be problems on election day, questioning whether the system will be able to handle so many extra voters.
Election officials in Virginia are stepping up security at polling booths amid concerns over long waits and issues such as voter registration and identity verification.
