In all the hoopla of last week's inauguration, there was an understandable lack of attention to another second-term swearing in, that of Frank J. Fahrenkopf Jr. as chairman of the Republican National Committee.

The Nevada lawyer, who took over the post midway through President Reagan's first term, has set an agenda for the next few years as ambitious in its way as the president's dream of cutting deficits, simplifying the tax system and ending the nuclear arms race.

As a loyal party man, Fahrenkopf endorses all those goals, but he has his heart set on an equally elusive target: overthrowing the seemingly permanent Democratic majority in the House of Representatives.

"Never say never" is good advice to political pundits, but a Republican majority in the House comes close to the Never-Never Land category. It has been one-third of a century since the GOP last won control of the House, in the 1952 election, and Fahrenkopf is realist enough to acknowledge that recovery will come only in slow stages.

What he told the national committee was that the pathway to eventual control of the House runs through the state legislatures.

Only by slowly and steadily building strength in the legislatures, in the elections of 1986, 1988 and 1990, Fahrenkopf argued, can the Republicans gain a large enough voice in the drawing of district lines following the next census to have a realistic possibility of taking over the House in 1992.

If this has a familiar ring, it should. Just four years ago, in the wake of Reagan's first win and the capture of the Senate, Republicans announced that they were going all-out with computers, consultants and cadres of lawyers to win the post-1980 redistricting battle. They had everything they needed but the votes -- and the Democrats clobbered them in most of the major states, including California, Florida and Texas, the largest gainers from the migration to the Sun Belt.

This time, vows Fahrenkopf, it will be different, and he cites his own experience in Nevada. "When I became state chairman in 1975, we (Republicans) were outnumbered 31 to 9 in the state house of representatives. Now, we have a majority of 25 to 17." What had been an all-Democratic congressional delegation at the start of the 1970s, now has three Republicans and one Democrat.

It is hard to argue with success, but there are people ready to challenge Fahrenkopf's strategy as unrealistic.

In a recent study of the long-term GOP prospects, conservative political analyst Kevin Phillips said of the Fahrenkopf plan, "To say that it'll be tricky to accomplish is an understatement."

Phillips pointed out that Republicans are starting from a historically weak base in the states. After Dwight D. Eisenhower's and Richard M. Nixon's second-term victories in 1956 and 1972, the GOP had 20 and 19 governors, respectively. Now it has 16. In 1956, it had full control of the legislatures in 17 states; in 1972, of 16 states; now, of only 11. Even though Republicans gained slightly over 300 legislative seats last fall, the first year in which Fahrenkopf's long-term, grass-roots plan was tested, they are still slightly below the levels of 1956 and 1972.

Nonetheless, there is an opportunity there -- and the emphasis Fahrenkopf is giving to the legislative and gubernatorial races in his plans almost guarantees that financial and organizational resources will flow in that direction.

The difficulty is that they may have to flow uphill against the pattern of history. As Phillips has pointed out frequently in his newsletter, The American Political Report, the midterm election six years after a switch of White House control to the Republicans has often seen severe losses for the GOP.

In 1958, six years after Eisenhower was first elected, Republicans lost 13 Senate seats, 47 House seats, five governorships and 650 legislative seats. In 1974, six years after Nixon came to the White House, the GOP losses were five Senate seats, 48 House seats, six governorships and 674 legislative seats.

Those defeats were associated with recessions and major White House scandals, neither of which the Reagan administration is necessarily doomed to suffer in the next 21 months. But the note of caution Phillips strikes is probably a necessary corrective to the extravagant claims of political realignment that some Republicans were making in the high spirits of last week's inaugural ceremony.

If nothing else, it should remind us that the Republicans have been here before -- within sight of the promised land of majority status -- only to be turned back by cruel fate or their own mistakes. And neither of those can be controlled by Fahrenkopf's planning.