And while the district voted for GOP presidential nominee Mitt Romney with 61 percent in 2012, there remains a third possibility that a Democrat can eke into a runoff if the second-tier Republicans carve up the conservative vote.
Operatives say Mayo, an African-American mayor of one of the district’s largest cities, would likely be the Democrat who could pull off that scenario.
However with other Democrats in the race, including state Reps. Marcus Hunter and Robert Johnson, the party would need to unite behind just one candidate for Mayo to be successful.
With a low turnout predicted for the contest, operatives say anything can happen on Saturday.
“Anybody that can successfully predict this special election should be a professional horse gamer,” one Republican said.
Former Sen. Scott Brown, R-Mass., candidate for U.S. Senate in New Hampshire, holds his hand over his heart during the singing of the national anthem as he waits to take the stage for his town hall campaign rally with Sen. John McCain at the Pinkerton Academy in Derry, N.H., on Monday, Aug. 18, 2014.