Richard Bryan is a first-term senator from Nevada, and the morning line says here is a man you should not bet against.

He is author of what has become called the Bryan Bill. It is a proposal that would make some major changes in the Corporate Fuel Economies (CAFE). Despite some reports to the contrary, neither Bryan nor CAFE are going away.The legislation was defeated by a scant margin during the last session of Congress. There is every indication Sen. Bryan is getting ready to do battle again. If he wins - and increased support might be considered likely with all the oil-related problems the nation faces - carmakers would be facing fuel economy standards of 40 miles per gallon by the year 2000.

This would mean that, under the present fleet mix, carmakers would increasingly be forced to market more and more compact and subcompact cars. Supporters say consumers want smaller, more affordable cars; the manufacturers say we want the bigger, less efficient ones.

Why the conflict? Surveyors point to the way each group asks the questions. Consumers are quick to say they want fuel efficiency. However, when asked what cars they like, very few list the current round of vehicles that can attain 40 miles to the gallon.

The current military and political standoff in the Middle East, and American balance of trade problems are the greatest motivating forces that keep CAFE on the front burner.

The Sierra Club points to the need to reduce global warming and other environmental considerations as well. But on that point, Thomas Hanna, president of the Motor Vehicle Manufacturers Association, says vehicles made in the United States account for less than 3 percent of harmful emissions worldwide.

Albert Slecter, lobbyist for Chrysler, also says there are plenty of small, fuel-efficient vehicles already in the marketplace and that they rarely are among the best-selling models.

Some of the answer, in the end, will depend on consumers. And what they buy. Some on carmakers and the engineering efforts they put into the cars. And some on politicians, who must weigh concerns for our trade deficit and the environment against the needs of the manufacturers and their sizable work force.

Robert Stemple, chairman of General Motors, says he fears that congressionally mandated smaller cars may cause consumers to keep their larger, older ones for longer periods of time. And, he adds, they are the least fuel-efficient and the greatest polluters. So, at least in the short run, the efforts could backfire before progress can begin.

Whichever side prevails, much will be at stake.

American carmakers misjudged the nation's desire for smaller, more efficient and better-built cars about three decades ago and lost a giant portion of the world market share to foreign manufacturers.

And now, with an economy slipping close to recession levels, a misjudgment on their, or Congress', part could have significant results as well.