Voters in an upstate New York congressional district will choose between a Democrat regarded by many as the natural successor to the longtime congressman who vacated the seat earlier this year and a Republican with crossover appeal in a special election Tuesday. Democratic Rep. Brian Higgins, who arrived in Congress in 2005, resigned in February to become president of Shea's Performing Arts Center in Buffalo. With Republicans holding a narrow margin in the U.S. House, even a race for a seat widely expected to remain in Democratic hands has drawn its share of scrutiny.