If he could get elected Governor again in 1978, he could run as a sort of "New Democrat" before the phrase was in use. A popular Southern Moderate to Liberal Governor with six years under his belt.
Not sure about his legacy, but assuming the economy comes under control similar to OTL, then there's probably much less stress between Carter and Congress. Thus, he's able to get energy and healthcare passed without the huge tension between him and Ted Kennedy, though Ted's ego might still get in the way. I can see a sort of strange foreign policy coming into play where Carter does the whole diplomacy, missile reductions treaties, etc., but at the same time works on fighting the Soviets in proxy-wars. After all, the first use of the Reagan doctrine was in 1979 against the Soviet invasion of Afghanistan, so maybe we get something like that under Carter. However, Carter's motivations probably wouldn't be beating the Soviets, instead, he'd probably cite human rights as his #1 concern there.
