It was really rather rude. There was the President, evidently impatient to get away, and there was a roomful of bellowing reporters. From long experience I sensed the problem. Mr. Reagan hadn't had a formal press conference since July 26, when he had his 19th. A kind of hysteria builds up. This meeting now, theoretically, was just a cursory occasion, called to introduce the new national-security adviser, Robert McFar
lane. But under the American scheme of things an interval of three months with no regular presidential give-and-take is a long time. Evidently Mr. Reagan sensed this himself. He met the press here formally Wednesday night, while this earlier affair was what the White House calls a ''quickie.''
The modest, oblong White House briefing room has about 48 seats like a motion picture theater. The color is blue. The President stands at the end on a little platform: He is ruddy and smiling.
Mr. Reagan now introduces ''Bud'' McFarlane, a man likely to be one of the most important influences in Washington and, for that matter, the world. He is a kind of alternate secretary of state. ''I wanted someone of strong principle and keen judgment,'' the President says. He emphasizes ''leadership,'' ''teamwork.''
Mr. McFarlane now speaks. He has a controlled, deliberate, confident manner. He is careful, slow, authoritative. He is attractive. He makes a favorable impression on the tense crowd. It is a little hard to explain the excitement of the moment. The departure of Interior Secretary James G. Watt was a shocker. His replacement by national-security adviser William Clark has also been extraordinary.
The President stands on the little platform with Mr. McFarlane, grinning as the press shouts. ''May I say that there was a lot of speculation and declarations that were based, again, on those faceless and nameless sources,'' he tells one reporter.
Newsmen shout from the side. They want to find out about a lot of things: ''Why are we in Lebanon?'' demands one questioner. ''Why are we letting our marines be there to get killed every day?''
''Because I think it is vitally important to the security of the United States and the Western world that we do everything we can to further the peace process,'' the President replies. He is evidently trying to disengage himself. He makes some ambiguous comment.
''Will you change policy now at all?'' cries a reporter from the sideline.
''No,'' says the President.
''Sir,'' says a questioner, ''a Soviet general is quoted today as saying that if you go ahead with the INF deployment, the Soviet Union will deploy new missiles that would put the US under 10-minute warning.''
''I don't exactly take a Soviet general's word as being authoritative on anything,'' he says curtly and makes a break and gets away, leaving Mr. McFarlane to continue. The latter does so, it seemed to me, in a careful, professional way that creates a favorable first impression.
On the larger stage, Mr. Reagan is at a critical juncture of his presidency. He has had some good news in the economy: Unemployment and inflation are down.
Other things are as confused as they are likely to get. There is fighting in Lebanon. There is turmoil in Central America. Relations with Russia have rarely been worse. We are hurrying toward a crisis on the deployment of US nuclear weapons in Europe. These matters are jumbled at home, with speculation on who will win the presidential election a year from now. Mr. Reagan is trying to override doubts and to inspire, or renew, public confidence. What will it be like a year from now? It seems a long way away.