I agree that third-parties do well in Maine. In 1992, Maine was the only state where Bush was third. Clinton was first and Perot was second.
I read that, usually, the strongest third-party presidential candidate takes votes from the incumbent party. In 2000, when the president was a Democrat, Nader got about 3%, helping a Republican win. In 1992, when a Republican was president, Perot got about 19%, helping a Democrat win. In 1968, when a Democrat was president, Wallace got 46 electoral votes, helping a Republican win.
I say Nixon would have won the Wallace states of GA, LA, AL, and MS if Wallace hadn’t run and, They voted for him in 1972 and they voted for Goldwater in ‘64, so why the hell would have voted for HHH in 1968? HHH came in 2nd in MS (by a significant margin), AL, and LA but I don’t think that matters, most of that Wallace vote would go to Nixon. He may have won the remaining Wallace state of AR too, it went for Johnson in ‘64 but Nixon edged out HHH for second.
I think Nixon probably would have also taken MD which HHH carried by a couple points. I doubt the result of any Northern state would have changed despite anecdotal evidence that Wallace hurt HHH in the North.
1968 with no Wallace, easy Nixon win, says I.