In Michigan, Rep. Jim Dunn tells voters he's tough, fair and independent. What he doesn't say is that he is a Republican.

In South Carolina, Rep. John L. Napier defends President Reagan's programs -- but only when forced to. He prefers to run as his own man who defends his congressional district against all comers.

In Ohio, Rep. Ed Weber, who voted for the major tenets of the Reagan economic program, dismisses charges that he always supports the president by enumerating a long list of his votes against Reagan, including the Olympic coin bill.

These three congressmen are members of the Republican class of 1980, a flock of 52 new House members who rode to Washington on President Reagan's coattails and now must answer to the voters for 10.1 percent unemployment and $100 billion-plus deficits.

The Class of '80 has been scorned in Washington as "Reagan Robots," alleged congressional clones of the president who vote with a rubber stamp, not an open mind. But back home, you wouldn't recognize many of them as such.

"What's interesting is how few of them are running as supporters of President Reagan," said Ann Lewis, political director of the Democratic National Committee.

That is no accident. On the advice of some Republican elders, many of the freshman Republicans have unzipped themselves from the Reagan administration and are now proudly displaying votes they cast against the president during their first two years in office.

Others who ran on the theme of lower taxes and getting government off the backs of the people are holding firm and criticize Reagan for going soft on Reaganism. They complain, in effect, that he's the one who is failing to "stay the course."

One is Rep. John Patrick Hiler of Indiana, who beat ex-House Majority Whip John Brademas and appears headed for reelection. His ads say: "He's doing the job he was hired to do."

Another is Rep. Denny Smith of Oregon, who defeated former House Ways and Means chairman Al Ullman in 1980 and is now running to the right of the president in a state with a history of moderate and liberal politics.

The common denominator in the campaigns of the freshman Republicans -- and the reason they appear difficult to defeat -- is their emphasis on service to their districts, not on the overriding issues that helped get them to Washington.

In Texas, Jack Fields, who knocked off Democratic Rep. Bob Eckhardt in 1980, reminds voters that he has been back home 61 of 84 weekends, held 90 town meetings, has given 134 speeches, attended 78 special events and 53 seminars. His only discussion of the economy in his ads is his support for accelerated leasing of the Outer Continental Shelf, which he says will create 10,000 jobs.

In Connecticut, Lawrence J. DeNardis's television ads are "oriented to the congressman's personal approach to his constituency," according to campaign manager Robert Parisi. DeNardis has no ads that discuss the economy.

As a result of this homespun approach, many of these Republicans are holding their own in districts that are either ravaged by unemployment or are historically Democratic or both. Unless a huge Democratic landslide materializes, an overwhelming majority is likely to be reelected.

Of the 50 freshman Republicans running for reelection, only about 17 are in competitive races. The others now appear safe, according to strategists for both parties.

"The interesting question is, why are certain people in competitive races?" says Nancy Sinnott, executive director of the National Republican Congressional Committee. "I think it's just hard work -- and in some cases opponents who are not too strong."

There is another historical factor that helps the Republicans. The Democrats may be optimistic in hoping they can defeat even a dozen GOP freshman, for they are bucking what has become known as the "sophomore surge," a trend in which new members are less vulnerable than their more experienced colleagues.

"Freshman congressmen seeking their first reelection have run 6 points better than other party colleagues," says Thomas J. Mann, a political scientist and student of congressional elections.

The best-known example is the Watergate Babies, the 75 Democrats elected in 1974. In 1976, 74 sought reelection and only two were defeated. Mann said the phenomenon began to show up in the late 1960s and has been true for freshman members of both parties.

House members elected in the last decade have devoted themselves to constituent service, much more so than their seniors. They go home more often, they send back more newsletters and they put a premium on taking care of problems of their district.

None of these freshman Republicans, especially those in competitive races, can avoid Reaganomics completely. When confronted with it, they are quick to blame Democrats for today's problems and echo Reagan's claim that many economic indicators are improving. But many GOP freshman have chosen to ignore the phrase "stay the course".

"Basically, our ads say we have to cut back, not with a meat ax, but with a paring knife," said Sally Riddle, Dunn's Michigan campaign manager. "People don't want a meat ax. In their minds, they associate that with Reagan. That's why Jim is battling him."