This is the guy who ushered in the neoliberal era; the guy they stuck in to suppress the left of the Democratic party, the first successful anti-McGovern candidate (whose slightly left-of-neocon positions were blamed for the loss of the previous election.) Carter left office as a failure, partially due to behind the scenes manipulation of the Iran situation by the Reagan campaign, but mostly due to the fact that there was no positive case to be made for his presidency either.
Carter was the bridge from the New Deal to Clintonism (with a brief stroll through the Party's destruction of the Rainbow Coalition), where the parties only ever differ on a handful of wedge issues. A merger that destroyed Democratic political dominance in the US, it didn't save it.
He should be celebrated for his post-presidency e.g. his work for Habitat for Humanity and for Palestinian rights. But Democrats should stop trying to retcon him. I expect the effort to increase after he is dead, since he will have lost the ability to remind them that he's been opposed to their policies on the Israeli occupation. I could swear he was getting bipartisan-ly smeared as an anti-Semite just 15 or so years ago.