At no point has Gingrich ever been a contender in any Presidential race. Getting on TV doesn't make you a contender. Even Herman Cain managed to do that.
Okay, then, the almost $500k/yr he was making a year in speeches and his active involvement and relative success in politically oriented consultancies. Take your pick. He's still being pretty damn successful in political spaces.
edit: ha - misspoke, it was actually almost $5M / year
edit: ha - misspoke, it was actually almost $5M / year