A liberal Democratic congressman from a large industrial state told a story the other day that helps explain why many in the House and Senate aren't yet embracing the new conventional wisdom that the Camp David summit has saved Jimmy Carter's political skin.

The story involves public works - a special favor this congressman needed from the Army's Corps of Engineers in his district. A matter of a few million dollars, an easy thing to do in the congressman's view.

"You know," the congressman recounted, "I should have been able to take care of this in one short meeting with Frank Moore," Carter's chief of congressional relations. "But I didn't even try. Frank Moore gives commitments and then they go up in smoke. He doesn't deliver. There's nobody down there [in the White House] you can sit down with and work out a problem like this one. You just can't count on them."

So this congressman - a man who has voted several times to support the president when that was not a popular thing to do - is looking for another solution to his problem, working through influential committees in the House.

Members of the House and Senate tell stories like that about the Carter White House all the time. These are politicians talking, many of them envious of Jimmy Carter because he - not they - grabbed the biggest brass ring in the political game, and now angry at Carter because he can't seem to keep the ring polished. It is difficult to find any politician in Congress who believes that Jimmy Carter is a good politician.

This is not the "eptness" issue that has had so much attention since the triumphal summit at Camp David. There seems little question that the president has done himself enormous good on that front. Camp David demonstrated that Carter is an effective negotiator, a master of intricate detail and a man of nerve. Those are qualities that his associates have been attributing to him throughout his presidency, and the summit at last provided an opportunity for them to shine. All those skills could contribute to effective political leadership, but none of them guarantee it, alone or together. That is Carter's problem.

Before Camp David there were serious conversations among professional politicians in this town abut the possibility that the Carter presidency might simply unravel during the coming year. According to one gloomy view, Carter's low standing in the pools could soon be accompanied by a period of runaway inflation, a collapse of the strategic arms talks with the Russians (or defeat or an arms-control treaty in the Senate), a disastrous fall in the value of the dollar and - by 1980 - a serious challenge for the presidency from Gov. Edmund G. Brown Jr. of California or Sen. Edward M. Keanedy (D-Mass), or both.

In fact, all of these remain possibilities - only the polls have changed. The congressman complaining about Frank Moore and the White House was speaking 10 days after Camp David. The president's indifferent oratorical skills have not apparently been influenced by his triumph at the summit. Carter remains unable to count on the support of any member of the House or Senate out of simple loyalty or admiration - he and his colleagues have up to win congressional votes one at a time, often by overcoming deep skepticism.The world's bankers remain suspicious - and in sometimes contemptuous - of the Carter presidency. They ran the dollar down another percent or so the day after the successful completion of the Camp David summit, and conversations with participants in this week's International Monetary Fund meetings here suggest the dollar remains extremely vulnerable.

In the long run, the administration's victory on the natural-gas bill may prove at least as important as Camp David in any resuscitation of the president's standing, if there is to be one. Although the bill the Senate passed Wednesday is a far cry from what Carter once said he wanted, winning that vote decisively was an unusual display of political leadership by the administration. It depended on the White House effort to change the minds of senators who were inclined to vote against the complex bill for a combination of grand and parochial interests. In Congress, at least, that is what politics is about.

One of the shrewdest politicians in the Capitol is Sen. Abraham Ribicoff (D-Conn.), who in 30 years has been a congressman, governor, cabinet secretary and senator. Ribicoff has a suggestion for Carter, based on his view of the president's few big victories in Congress this year (the Panama Canal treaties, the plane sales to the Middle East, the natural-gas bill). Carter won those votes because he effectively made a case that each was in the national interest, Ribcoff believes. If he is to succeed in the future, the senator argues, Carter must fight only for similar reasons, abandoning his early, universalist hopes that his presidency could do all things for all Americans. Inflations and energy, says Ribicoff, are the only two issues that the president should worry about in 1978-79, plus a strategic arms treaty if he can negotiate one.

Whether or not this is the right prescription, it is a good example of the feelings in the Capitol about Carter's political fate. The consensus is that, despite Camp David, Carter's record thus, far is dominated by his failure to exercise effective political leadership. Professional politicians sense that this is a potentially fatal failure.