LET me be the first (and, perhaps, only) observer of the political scene to suggest that if the Democrats want a potential presidential winner, they should take another look at a fellow who took them there before: Jimmy Carter.I have no idea whether Carter would even be interested. But not too long after he had left the White House I asked him whether he might run again. "After all," I said, "you are eligible for another term." He only smiled and acted as though the question was irrelevant. But when I hear Democratic strategists and pundits say the only way Democrats can win the presidency is with an outstanding candidate - and bemoaning the absence of one - I wonder why no one thinks of Carter. New York Times columnist Tom Wicker says the party needs "a modern version of FDR - a candidate who knows where he or she wants the country to go and how to get there; who can persuade the public to go along, take the blows of a campaign and hit back harder." Well, Jimmy Carter proved in 1976 that he was just that kind of a man. Why is he completely ignored? The answer, I realize, is obvious: The Democrats and most observers have bought the widespread verdict on Carter as he left the White House - that he had been a weak and ineffective president. The Republicans portrayed him as such as they swept into power. But it was the Democratic liberals who never had backed Carter who were particularly happy to adopt this "Carter-as-failure" assessment. They tried to beat Carter in the 1980 primaries and only succeeded in weakening his campaign against Reagan. This liberal, anti-Carter view has since seeped into political columns and books on the Carter administration. I think the Democrats would be smart to take another look at Carter. As I write this, he is in New Orleans helping to build housing for the poor. He could be playing golf or going horseback riding or spending his days in opulent surroundings among rich friends. But not Jimmy. He's out helping the poor and disadvantaged. And he's not bragging about it. He's just doing it. No matter what the Democratic strategists may think of Carter (and it seems they aren't thinking of him at all), they should take another look at a very bright, sincere, and caring fellow. They'd find that the American people today have a high regard for him. The Carter image of 1976, tarnished by the hostage crisis and an administration that was said to be in a malaise, has been refurbished. Carter has done this by demonstrating his genuine interest in helping people and not by spending his latter years profiting from his presidential name. Carter's presidency, too, is being upgraded from earlier, unfair appraisals. As Jim Baker moves around the Middle East in his effort to pull the parties together and achieve a settlement, one has to be reminded of Carter's accomplishments at Camp David. Who else, as president, has pushed harder for human rights around the world? During the Gulf war it was recalled that Carter proposed and worked for a policy that could have led to US energy independence and might have averted that conflict. True, there were all those Cuban criminals that Castro shipped into south Florida - and whom Carter let in. Yes, Carter had his deficits. What president hasn't? Anyone who traveled with Carter on the campaign trail or watched him closely as president should remember what an engaging fellow he was - his compelling smile and earnest manner. He not only understood the intricacies of every issue, he could convey them knowledgeably to others. No, the Carter who left Washington in '80, depressed by his loss and by the way critics were putting his presidency down, couldn't make a good run of it. But there is a new perception of this valiant fellow among Americans. Bolstered by that, Carter could give the Democrats just the kind of candidate they need - if he were willing to take on that burden once again.