WI Colin Powell ran for President in '96 (he declined due partly to his wife's problem with clinical depression). Could he have beaten Bill (possibly with William Weld or Thomas Keane as his running mate).
As a Republican? Odds are he'd lose in the primaries. And the reasons he didn't run are more complex than you state, with his wife's problems not being very high on the list.
Assuming he did win the primaries, he would have a solid shot at beating Clinton.