Newt Gingrich’s prospects for the Republican presidential nomination may well rest with voters such as Jim and Karen McAfee

Mr. Gingrich spent little time courting voters in Michigan and Arizona, which are holding primaries Tuesday. That rachets up the pressure to win the March 6 primary in Georgia—the state with the most delegates on that Super Tuesday—or his presidential hopes could be over.

He has poured more money into his campaign here than anywhere else, with his staff of 12 outnumbering those of his chief rivals. He has won far more endorsements from state GOP officials than Mitt Romney and Rick Santorum.