Split-ticket voters were declared extinct. They may decide the Senate.

In recent election cycles, party loyalty – and deep suspicion of “the other side” – has meant fewer voters willing to split their vote. But this time around, they could decide control of the Senate.

While parties and pundits may cast America as neatly lined up into tribal camps, competing in a zero-sum contest for the future of the republic, allow Richard Bink to break the mold.

The Savannah, Georgia, veterinarian voted early at Islands Library here on Georgia’s Whitemarsh Island as ibises veered through an ultramarine sky. He usually...