THREE YEARS and one week after Rep. Morris K. Udall (D-Ariz.) suspended his 1976 presidential quest, the Federal Election Commission's auditors are still quibbling about how some of his campaign funds were handled. The FEC has pursued the matter so doggedly that you would think millions of dollars had vanished without a trace. Not so. Out of the Udall campaign's total expenditures of $5,166,015.37, the current arguments involve $74,135.69 - less than 1.4 percent.

In most fields of government spending - military procurement, for instance, or public welfare - an error rate of 1.4 percent would be considered very good, if not downright miraculous.But where public campaign subsidies are involved, the nit-picking seems to have no end. In the Udall case, the auditors want more documentation for outlays of $61,741.87, made up of about 280 separat items in 20 states. For almost all of these, Mr. Udall's people have provided canceled checks and an explanatory note such as, " $200 to Jane Smith - field expenses." The auditors won't accept that. They want a detailed bill, voucher or explanation from Jane Smith - who might have been a student volunteer. And what if Jane Smith can't be found to verify that the $200 really went for food, lodging and gas? Well, then, someone will have to reimburse the federal treasury.

The Udall campaign is not the only victim of this ludicrously slow, small-bore auditing. Two weeks ago President Carter's general-election committee was told to repay about $15,000 for poorly documented Election Day expenditures. The wrangling over some of George Wallace's campaign spending has also gone on longer than the campaign did.

Meanwhile, of course, a flock of presidential aspirants has already begun next year's campaigns. Do they have to anticipate having their New Hampshire expenses challenged in 1983? If that occurs, the FEC - which has already worn out everybody's patience - could bring the whole experiment in public financing into disrepute. True, some of the problems do flow from the law. If there were no state-by-state spending ceilings, for example, the Udall team would not be quarreling with the auditors about how much of his radio and television ads on Boston stations were aimed at New Hampshire voters as opposed to Massachusetts ones. But the undeniable complexities and quirks and unrealities in the law do not excuse the FEC. It has made a large contribution to the bureaucratizing of federal campaigns - and created a large agenda of difficulties for congressional committees to address.

To see what's gone awry, remember that the point of the "reform" was to open up presidential politics and encourage ordinary citizens to play a larger role. And now the larger role is that of lawyers and accountants - and citizen volunteers are being asked, three years later, to come forward with itemized receipts for every hamburger they bought on the campaign trail.