The peculiar mood at last week's Republican National Committee meeting here was reflected in surprising sentiment for a 1980 run for president by a junior member of Congress who six months ago was unknown nationally: Rep. Jack Kemp of New York.

The consensus of the most ranquil national committee meeting in memory was desire for a new Republican face, and the new face likely to have finished first in a secret ballot of committee members was Kemp. A leader of the national tax revolt as sponsor of the Kemp Roth tax-reduction bill, non-candidate Kemp has surpassed a half dozen potential candidates in bringing a sense of excitement to all kinds of Republicans.

The patently unrealistic Kemp-talk processed from Republican apprehension over what realistically lies ahead. National committee members view as the worst thing that can happen to their party a renewal of the 1976 struggle for the presidential nomination between Ronald Reagan and Gerald Ford. The second worst thing, they believe, is front-runner Reagan. "I love Ronald Reagan," said Massachusetts Chairman Gordon Nelson, a 1976 Ree of primaries, what national committee members say and do counts for much less than in bygone days. But abhorrence of a Ford-Reagan clash is pervasive among all Republican. When National Chairman William Brock met with the party's big money men here, their message was unmistakable: We want neither Reagan nor Ford.

That was the discordant note of a gathering free of controversy and approaching euphoria. Committeeman Clarke Reed of Mississippi, usually embroiled in contentious rules disputes, did not even show up for the first day of rules committee meetings. Iowa Gov. Robert Ray, lost in the labyrinthine Detroit Plaza Hotel, missed the entire executive committee meeting; it adjourned after 20 minutes, discussing whether a mid-Jaunary national committee meeting would interfere with winter vacations.

Accompanying the harmony was delight over Jimmy Carter's discomfiture. But when they considered opponents for him in 1980, their smiles faded.

There is no support for a Ford comeback. Even the former president's ardent supporters flinch at word from his advisers that he will run if necessary to stop Reagan's nomination - perhaps entering presidential primaries. The old pro-Ford majority on the national committee is now mainly anti-Reagan.

A diehard faction of Reaganites remains. Louisiana State Chairman John Cade typifies this hard core, who have no doubts about Reagan's age or electability. But there are more doubters among the faithful than the Reagan," said Massachusetts Chairman Gordon Nelson, a 1976 Reagan backer, "but I ask myself: should a 69-year-old man be running for president?" Nelson wants a younger man: Kemp, 43, or preferably Rep. Philip Crane of Illinois, 47.

What Nelson blasts out on the record, others whisper in private. I'll back Reagan, of course, if he runs," one mid-western committeewoman told us, "but I wonder what we're telling the young people of the country if all we have is Reagan, Ford and John Connally - three old men." Her choice: Kemp.

Kemp's undercover admirers are not limited to old-time Reaganites. He is admired by liberal GOP leaders in Michigan, who pray that favorite son Jerry Ford will not try again. Apart from his primacy in the tax revolt, Kemp transcends ideological splits. With Mississippi's Republican wounds from the Ford-Reagan struggle still not healed, Rep. Thad Cochran has asked only Kemp - not Ford or Reagan - to go there and help his Senate campaign.

Reagan operatives Lyn Nofziger and Dave Keene were here but maintained a low profile. They feel the problem will solve itself. Kemp has promised not to run against Reagan; other prospects attract only scattered interest.

Yet the mood here must concern Reagan. Several conservative committee members gathered over drinks to confront the age problem. What about Charles de Gaulle? Winston Churchill? Konrad Adenauer? "But none of them had to run for president in America," replied one committeeman - a sobering note for the party's front-runner.