It might be heresy to think, let alone say it aloud, in this one-industry town awash in the bonhomie that attends the convening of a new Congress.

But in the air of Capitol Hill this week there's a feeling, call it vibrations, if you will, that seems so thick and pervasive one might cut it with a knife.

The air is negative, notwithstanding all the jolly new-member receptions, notwithstanding the 414 inches -- more than three full pages -- of opening day coverage in this newspaper.

The temptation is to dub this the Negative 96th, for it is a Congress that is being asked, unlike its other recent predecessors, to say "no, no, no" and no again.

Two years ago, when the 95th began, it was with a new Democratic leadership and a new Democratic president, leading toward new initiatives and new directions.

Four years ago, when the 94th began, it was on the heels of the Nixon-Ford administrations, and it gave rise to the so called Watergate class in the House -- energetic and reform-minded youngsters who wanted to clean up Washingon.

But pendulums swing constantly, and now, as one congressional staff veteran put it, "This new Congress may be very typical of what you call Middle American.... This year we're back to a run-of-the-mill Congress -- not a lot of unguided missiles or cannons rolling around."

That view holds that the big concerns are the economy and inflation -- issues that require saying "no" to big spending and excess -- and that most of the legislative mountains have been climbed, at least for now.

Look at the agenda of the 96th Congress. Efforts will be made to resurrect failed ideas of the 95th, but the larger pending business will require clenching of jaws and saying no.

Cut federal spending. Control hospital costs. Deregulate the trucking and railroad freight industries. Reduce welfare costs. Hold the line on minimum wages. Regulate the drug industry. Find a way to finance Social Secutrity. Slow the nuclear arms race.

All of this requires, in one way or another, saying no. The new members know it. The old members know it. House and Senate leaders are not sounding electric trumpet-calls to action, nor is the president.

"What you have around here is a sort of air of distress," said another longtime congressional staffer. "It hasn't been 'fun' for the last couple of Congresses, and now it has reached a kind of distress level."

A little heavy, perhaps, but what he's talking about really is a certain loss of innocence. Take the economy -- a sense around Capitol Hill that the classic old theories don't work, and, even if they did, Congress wouldn't have that much impact anyway.

"What they know is that there's not much they can do about it. They know that the behavior of your big companies, a General Motors, say, has more to do with the way things are than Congress does," he went on.

All of this is subjective, of course, and it may just as easily be argued that one man's negative is another man's positive.

So when President Carter says that the 95th Congress achieved the bigger part of his legislative needs, and when the leadership says this will be an "oversight" Congress, reviewing the work of years past, they are talking about saying no on a variety of issues.

Somebody caught the essence of it at one of those many Monday afternoon libations around the House side, where constitutents and cronies gathered to lift a toast to the 96th.

They were having a swinging time at the party, hosted by Rep. Michael O. Myers (D-Pa.), where a Mummers string band from Philadelphia helped with the gaiety.

One of Myers' House colleagues started dancing, and a bystander shook his head. "They're having a good time," he said, "but Lord, you have to get three-fourths drunk to blot out what you really know about this place."