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.
Vice President Joe Biden waits to conduct a mock swearing-in ceremony with Sen. Brian Schatz, D-Hawaii, in the Capitol's Old Senate Chamber, December 2, 2014. Schatz was sworn in to serve the remainder of his term since he was appointed to the seat after Sen. Daniel Inouye, D-Hawaii, passed away.