President Carter's Camp David spectacular has strengthened his faded appeal among voters in this quintessential mid-America town, but summit success is only the thinnest veneer covering deeper problems of inflation, high taxes and big government.

Indeed, our political scouting her with the help of Patrick Caddell's expert field staff and a questionnaire prepared by Caddell's Cambridge Survey Research revealed some voter skepticism even on Carter's Mideast peace efforts.

"It's looking as if the summit at Camp David is not working out like it first appeared," said a 49-year-old housewife whose husband is a maintenance man at the John Deere plant. Although agreeing that the submit was the best single thing Carter has achieved as president, she quickly turned to what really matters: inflation.

That refrain became familiar in our interviews with 63 registered voters in Dubuque's 18th Precinct, a pleasant, lower-middle-income workers' suburb that split about 50-50 in the 1976 Carter-Ford presidential election, almost exactly as did the state of Iowa. The voters we sampled reflected the same 1976 voting pattern.

Despite recent findings by reputable national polls that Camp David at least temporarily turned the president's political fortune around, voters here were more restrained. Only a third of them agreed that Carter's performance "during the last month" has improved, while 10 surprisingly rated his performance as "worse." Almost half the total - 31 voters - saw "no change" in performance despite Camp David.

Likewise, the president was given an "excellent" performance rating by only one voter, while almost 57 percent rated him as "poor" or "only fair." A talkative, 34-year-old iron worker spelled out the president's continuing problem this way: "That summit thing was just done to put a feather in Carter's cap. He should do something about the cost of living the job situation." A 22-year-old chemical plant employee praised the "headway" at Camp David, but said the United States "should be more concerned with its own problems."

Largely on the basis of Carter's new assertiveness with Congress and his mediator role in the Arab-Israeli struggle, three voters who backed Gerald Ford two years ago have now turned to Carter. But three times that many said they would switch their 1976 Carter vote to Ford if the election were held today.

That pinpoints this conclusion: Neither Camp David nor the president's recent hard line with Congress - his successful veto of the defense-authorization bill and his apparent breakthrough on gas deregulation - has fully rehabilitated him in this moderate-conservative area.

To our question "Do you think the president deserves a second term?" fully half of those who backed him in 1976 either said no or were uncertain. Altogether, our voters divided on the second-term question this way today: 25 yes, 21 no and 17 undecided.

The president's handling of inflation was clearly an overriding reason, with "strong disapproval" expressed by 22 voters, "some" disapproval by 13. These disapproving voters far outweighed the 14 who approved the administration's anti-inflation campaign.

The Achilles' heel of inflation is only part of the president's vulnerability on economic issues. For example, we asked whether Iowa needed new limitations on state taxing powers similar to California's Proposition 13, a symbol of taxpayer revolt. Only eight voters did not know about Proposition 13. Of the balance twice as many favored a Proposition 13 - style tax limit as opposed it, even though Iowa is far from the top of the list of states afflicted with high property taxes.

Other issues weighing down the president's standing include negative approval ratings on his handling of the Soviet question and national defense, with a 50-50 rating on his farm policies. Of all the issues on our questionnaire, Carter did well only on the Middle East, with a solid score of close to 90 percent approval.

"What he did at the summit may make world peace possible," a 44-year-old Dubuque packing company worker said in praise of the president.

But what the bulk of our voters made vividly clear here was the Middle East, with or without eventual success of the Camp David summit, cannot come close to sustaining Jimmy Carter's recovery from his 19 months of grave political troubles. If the White House holds a contrary view, it is baking pies in the sky.