Tucked away in the trunk of the Chrysler aid bill as it careened through Congress in December was an inconspicuous amendment that could give a significant boost to the development of the electronic automobile.

Few Senate and House members knew they were helping electric vehicles in the pre-Christmas rush to pass the Chrysler bill, said Sen. James A. McClure (R-Idaho), who engineered the maneuver and cannot restrain a chuckle about it three months later.

Officials at the Department of Transportation were surprised, as well, to find the amendment in the bill, they say.

McClure's idea was to give the major automakers a new incentive to speed mass production of electric cars and vans. The industry has been predicting that day would arrive sometime between 1985 and 1990.

The automakers are being squeezed hard now by federal fuel-efficiency requirements, which compel them to steadily improve miles-per-gallon performance of their vehicle fleets, reaching an average of 27.5 mpg by 1985. Because the average applies to an automaker's entire line, the more small, efficient cars produced, the more large gas guzzlers the company can make.

If electric vehicles were included in the calculation, McClure reasoned, the automakers' task of meeting the mileage standard would be eased considerably. EVs run on batteries and use only small amounts of gasoline for heating.

McClure proposed a complicated formula to calculate the amount of oil burned by utilities to generate the electricity needed to recharge batteries of electric vehicles. The oil figure would produce a miles-per-gallon rating for EVs. He estimated it would be over 140 mpg.

But his proposal, introduced in the Senate a year ago, went nowhere. The same was true in the House, where Rep. Tom Corcoran (R-Ill.) and 25 cosponsors introduced a companion bill.

"It was new. They didn't understand it. That makes it harder to sell," McClure said. Corcoran couldn't even get hearings held on the proposal last year.

Then came the Chrysler bill. McClure, Corcoran and a few other sponsors persuaded the House and Senate members handling the Chrysler bailout that their electric vehicle bill was harmless. It might do some good. bIt couldn't do any damage.

The amendment passed the Senate and was accepted hastily by Senate and House conferees. "They didn't focus on it as carefully as they might have," McClure said of his Senate colleagues. One reason may have been that the amendment in its first paragraphs appeared to be just another energy study of electric vehicles.The language requiring the government to include EVs in the fuel economy standards was buried in the fine print.

It wouldn't have passed any other way last year, McClure said.

"I don't think it was an end run," said Paul Brown, who heads the Energy Department's electric vehicle program. "It was just good, practical politics."

The Energy Department supports the concept, he said, and is working with DOT and the Environmental Protection Agency to set a miles-per-gallon figure for EVs by next month.

McClure, understandably, believes his notion has advanced the arrival of electric vehicles significantly.

"General Motors has shortened its timetable and that's a direct response, I know,' McClure said."We'll find a number of them on the roads by 1983."

McClure, like other electric vehicle advocates, believes that a sizable market for EVs already exists in central cities, where they can be used as second cars, for commuting, and their limited range and speed won't be a serious drawback.

An auto industry official involved in EV development agreed the pace has quickened, although that has more to do with accelerating improvement in battery technology than with McClure's bill, he said. But when the automakers reach a decision on when to begin mass production, the decision is likely to be a close one, the official said. And McClure's bill could tip the balance in favor of electric vehicles, he said.