It was nearly a crisis. The gray tweed coat worn by Roger Mudd in Washington was a dead ringer for the gray tweed coat worn by Tom Brokaw in New York. And this during the week in which Teddy Kennedy and Walter Mondale had been referred to, on the Mudd-Brokaw (or Brokaw-Mudd) report as "Tweedle-Dum and Tweedle-Dee."

America's newsome twosome need to work on coordinating their fashion ensembles, but that seemed to be about the only noticeable problem on the first week of the new "NBC Nightly News," with Brokaw replacing John Chancellor in New York, Mudd promoted to co-anchor from Washington and Chancellor now relegated to the ivory tower of commentary.

High network hopes are pinned on the boy baritone and the woodsy sage--a kind of city mouse-country mouse combo--who are trying to do for NBC News in the '80s what Chet Huntley and David Brinkley did for NBC News in the '50s and '60s. The first week of the program, which is produced by Paul Greenberg, was not particularly flashy or spectacular, but it did seem awfully seasoned and assured for a substantially new news program, as if it had already been running in its present form for several years.

It was civilized, brisk, tony, unpretentious, alert and both solid and slick. And it was comfortable; it's an easy show to be comfortable with. The hard-core competitive question is whether the chemistry generated by the new team will be electric enough to overtake the "CBS Evening News" for the number one spot in the daily news ratings.

The animated globe opening for the show somewhat resembles the animated globe opening that "CBS Evening News" recently threw out. On opening night, while the NBC announcer was still unreeling the complicated introductions, Dan Rather was already into his lead story on CBS--a report on the situation in the Falkland Islands. But the new sets in New York and Washington, designed for NBC by Gene Cesa, are models of functional simplicity. Brokaw appears on the right of the screen with superimposed graphics on the left; Mudd's on the left with the graphics on the right. The show bounces back and forth naturally and effortlessly--although Brokaw still hasn't quite mastered the art of saying "Roger?" when it's time to throw it to the capital.

Even though Congress was not in session during the first week of the new newscast, and there was little hard news from Washington, it seems clear that Mudd will be the dominant half of this news team. He has more authority, more intimacy and more laconic flair than his partner in New York, and he doesn't suffer from the stigma of pretty-boy glamor that Brokaw carries with him. Mudd is a real writer, and he brought distinctive touches to such stories as the burning of Wolf Trap ("Tonight, Wolf Trap is a capital loss") and the inability of Alexander Haig to appropriate an airplane to take him to England because so many congressmen were off on joy rides about the globe.

The legislators call these trips "fact-finding missions," Mudd noted, but to the rest of the world they're known as "junkets." Mudd has a way of delivering such facts with a subtle sarcasm that never seems smug. He is a stylist as well as an expert, which puts him two up on his younger colleague.

If the "CBS Evening News" is to be the broadcast of record, as it traditionally has been for more than a decade, NBC's could be the newscast of character. If there's going to be a slight spin on the ball, Mudd is certainly the one to supply it. The chemistry between Mudd and Brokaw suddenly seems less important than the chemistry between Mudd and the viewer, and there is a possibility that many viewers will find Mudd a less insistent and more attractive news giver than the dynamic Rather on CBS.

Since Mudd seems to be the key to the success of the broadcast, the program's seesaw billing is a bit ironic. On the nights when the lead story is from Washington, Brokaw gets top billing followed by Mudd, who then delivers the opening story. This flip-flops on nights when the lead story comes out of New York. In addition, an exactly equal number of promos have been prepared and shown on the air in which Brokaw and Mudd again take turns at top billing.

If memory serves, there was never any debate, once the program was on the air, about whether it would be called "The Huntley-Brinkley Report" or "The Brinkley-Huntley Report," even though Brinkley, like Mudd, was the star of the show. But that was in less fervid times. NBC News spokesmen love to point out that Mudd and Brokaw are old pals who love each other like brothers, but the fact is they have agents, and agents are like divorce lawyers. They always come out fighting, and they push their clients as far as they can.

The fuss over the billing is an embarrassment, and it should be both to Brokaw and Mudd. One would like to think that Mudd's face would get redder over this than Brokaw's. But the first week made it quite apparent that the new "NBC Nightly News" is going to give the "CBS Evening News" not only a run for the ratings, but a run for the prestige. It's commonly conceded that newspapers thrive on competition and suffer when they have none; so there is no reason to deride competition between two television networks, each trying to produce the best and most popular evening newscast. It could be a fascinating and even beneficial contest.

Early ratings for the new "Nightly News" are not conclusive. But an NBC spokesman said Friday that "most people are walking around here with broad smiles. Everyone here seems very, very pleased with it." He said producer Greenberg was seen smiling after Monday night's broadcast--"I think for the first time in two years." Greenberg has produced the program since 1979. The promotional slogan for the new show is "Experience you can trust," and that doesn't seem too flamboyant a claim at all. Both CBS and NBC are now airing first-class newscasts each night; it would be nice if they could be content with "first-class" and worry less excessively about being first.

ABC also has an evening newscast. It is called "World News Tonight."