George Wallace carried 5 states and won 46 electoral votes as a third-party candidate in 1968. In the 1972 election, he ran as a Democrat and was a leading contender, which was intolerable for the Establishment. So a mysteriously funded Lone Nut shot him five times.
Wallace ran as a democrat.
I seem to remember he carried a number of primaries (Michigan? rings a bell)before he was shot.