THE BALTIMORE SUNWASHINGTON -- Bill Clinton and Jimmy Carter, the only Democrats elected to the presidency in the last three decades, have long had a complicated and awkward relationship which was underscored by Carter's controversial diplomatic mission to North Korea last week.Carter's statement that his talks marked a breakthrough in tense U.S.-North Korea relations raised the tension level again as White House officials sniped at Carter for going beyond the current U.S. policy.Carter's defeat at the hands of Ronald Reagan in 1980 ushered in 12 years of Republican control of the White House. Carter returned to Plains, Georgia, intent on rehabilitating his name. His work has paid off. Through the Carter Center in Atlanta, he has helped monitor elections around the globe, earning him an international reputation. Habitat for Humanity, his charity, has built homes for poor people, earning him a reputation for caring. Emphasizing human rights, for which Carter was once ridiculed, has become routine in American foreign-policy decisions. And as Carter's approval ratings have improved, historians, too, have expressed kinder words. Presidential scholar Stephen Ambrose has publicly declared Carter "the most successful" ex-president in modern American history. But at the Clinton White House, Carter's reputation has not been entirely redeemed. There, Carter has one gigantic mark against him, one that overwhelms all of his good works. "He lost his re-election campaign," one Clintonite explained succinctly. Over the weekend, when Carter returned from North Korea, Clinton, at the presidential retreat at Camp David, Maryland, only talked to Carter by telephone, sending aides to debrief him at the White House. Carter appeared to get out in front of the president in a way that caused confusion and made the administration look weak -- its worst fear.Carter, visiting North Korea to discuss that country's alleged pursuit of nuclear weapons, announced that the United States would not continue to pursue sanctions against North Korea. He announced that the North Koreans had agreed to freeze their nuclear program and dropped the news that they wanted a summit with South Korea.The Clinton administration, however, was still pursuing sanctions, a policy Carter characterized as a mistake. Although the administration insists it is still rounding up support for sanctions, State Department officials concede that, because of Carter, that policy has taken a back seat to the summit. Publicly, the Clinton team says it has no problem with this development. "We have, surely, something to gain by talking with the North Koreans, by avoiding further steps toward a crisis," Clinton said Monday. "But we have to know there's been a change. So we'll be looking to verify that."Privately, angry White House aides believe Carter may have manipulated the situation so that he gets the credit for a breakthrough, but if the North Koreans are just stalling, the Clinton team will look naive and bumbling.