Upstate New York voters may be experiencing a sense of déjà vu, as state election officials prepare for the possibility of a third special election in the wake of Democratic Rep. Eric Massa’s planned resignation Monday amid allegations of ethical improprieties. But unlike in the two recent New York special elections, which Democrats won in Republican-friendly districts, Republicans are feeling bullish about their prospects for winning Massa’s seat, given the circumstances surrounding the vacancy and the conservative nature of Massa’s western New York district. Republicans hold a 45,000-voter registration advantage in New York’s 29th District, and it is one of...