Last night, for the first time during his presidency, Ronald Reagan made a prime-time speech to the American people and the nation's three major television networks decided to tune him out.

Instead of Reagan at 8 p.m. EST, NBC opted for Andy Griffith in his role as Matlock. Instead of the president talking about the need for $36.2 million for the contras, CBS offered its new news feature, "48 Hours." Instead of Reagan automatically preempting the standard evening TV fare, ABC stuck with "Who's the Boss?" -- a pertinent question given this latest bout between the media and the nation's number one politician.

For the networks, the decision was simple, representatives of all three said yesterday. They were told that Reagan's speech contained nothing new. They had already covered Reagan's radio address on Saturday, plus two other similar speeches he's made in the past few days, and had offered numerous other news segments giving various views on the contras.

As CBS Washington Bureau Chief Joe Peyronnin put it: "This speech is really an argument more directed at a small group of people on Capitol Hill than at 200-plus million Americans."

So, the executives decided to cover the speech later, as news, not to carry it live during their peak hours for providing entertainment, news features and advertising.

The decision by the networks did not mean that the interested viewer was necessarily deprived of the president appearing live and unedited. Cable News Network agreed to carry the speech. And the networks made it available to their local stations in case any of them preferred it to their regular programming. Conus Communications also offered Reagan live to any of the nation's 700 local television stations at no cost, a promotional gimmick for its new video wire service.

But being shut out by the big three sent shivers through this media-savvy White House and left some political experts wondering whether this was another signal that Reagan is losing his clout in the waning months of his presidency.

Chief of Staff Howard Baker issued a statement late yesterday that said: "It has been the traditional right of presidents of the United States to communicate with the American people on important issues over television.

"The decision by the three commercial networks to refuse this opportunity to the President represents an attempt to substitute their judgment for that of the President on what the country should have the opportunity to hear."

White House spokesman Marlin Fitzwater added: "My own view is that it's an incredibly narrow interpretation of their public service responsibilities and a relatively arrogant news judgment."

Networks have pulled the plug on presidents before, including this one. Reagan was turned down when he wanted six minutes in mid-afternoon Oct. 14 to talk about the failing nomination of U.S. Appeals Judge Robert Bork to the Supreme Court. The networks also rebuffed a presidential request for a noon slot on June 24, 1986 -- also to talk about the contras.

But basing the decision on whether the president had anything new to say, Fitzwater said, "seems to me to totally ignore the historical significance of this vote" today in the House.

He noted that one NBC spokesman had said the network had done enough stories on "Iran-contra," which is something different than contra aid. "I rest my case," said Fitzwater.

Network spokesmen, however, emphasized the difference between a president's formal request for air time for a matter of importance or national security and the announcement that he would be in the Oval Office speaking, if cameras wanted to attend. The former is honored almost automatically, several spokesmen said.

"Does the president have a right to make a closing argument on his contra aid package? Of course, he does," said ABC White House correspondent Sam Donaldson. "But we have a right to exercise news judgment. And since there apparently is not anything new here, I think the networks made the right decision."