I could see MLK becoming President in 1976 if he hadn't died, but I sincerely doubt he would have wanted to be President. He was an activist, not a politician.
If he felt that civil rights progress had stalled in the '70's and 80's, I could see him doing a 3rd party run to try and deadlock the EC so that minority representatives in the House could negotiate something better. But in terms of truly wanting to be a politician, that was not his style.
Reagan/Bush 214 (39.2%)
Carter/Mondale 192 (37.3%)
MLK Jr./Anderson 129 (22.5%)
