Washington — Moderate Republican senators this fall could replace the liberal Democratic senators of 1980 as the political lightning rods of American politics.
This marks a significant turn in US political affairs.
Two years ago, it was liberal Sens. Frank Church of Idaho, George McGovern of South Dakota, Indiana's Birch Bayh, Wisconsin's Gaylord Nelson, targeted by conservatives, who fell victim to the Reagan/GOP sweep.
Now, it is the half-dozen GOP moderate senators, who must explain a delay in economic results from Reagan programs, who will be most closely watched.
''Several rather decent and good moderate US senators are going to have a very hard time answering the voters' question: Why should they vote Republican if it's a signal to Ronald Reagan that what he's doing is correct, and he should do more of the same?'' says Democratic pollster and election strategist Peter D. Hart. ''It's not that their own performance is dilatory, deficient. But the moderates could be the victims of the Reagan administration record.''
''Small issue'' politics of 1980 - conservative issues like abortion, school prayer - have been overwhelmed by ''big issues'' like the economy and recession in 1982, endangering moderates in less safe GOP seats, the political experts say.
Republicans acknowlege their party's moderates will face more problems this fall than conservative GOP candidates. Some think Reagan himself may be less of a burden to candidates. ''Do not underestimate that man,'' says Vincent J. Breglio, executive director of the National Republican Senatorial Committee. ''He's going to show more of an ability to pull out of adversity than people think.''
''Interest rates will be the critical variable,'' Mr. Breglio says. ''Interest rates are cutting more against baseline Republicans than unemployment is. With unemployment, you lose the Democratic vote that is less ours anyway. Without interest rates down - the prime rate, say, approaching 13 percent - even if inflation is 6 percent, we will be in trouble. A lot of our voters are 'doers.' They want to buy autos, boats.''
A Monitor survey of the 33 Senate races set for this fall shows the Democrats , on statistical grounds, potentially able to repeat the Republicans' 1980 feat of winning two-thirds of the races. This would mean, with the Democrats having 21 incumbents up and the Republicans 12, that the Democrats would hold even - upsetting earlier predictions of further deep Democratic losses.
At this stage of the race, no one is predicting the Democrats could make up enough ground to overcome their 53 to 47 disadvantage in Senate seats and regain control. Mr. Hart sees the Democrats losing one seat. Mr. Breglio sees the Republicans still able to pick up three. But gone is the Republican talk of a few months ago that the GOP would win enough Senate seats this year to lock up Senate control for the decade.
The sense in Washington is that the conservative tide has stalled.
''1982 will be a better incumbent year than any in the past decade,'' says Hart. ''From 1970 to 1974,'' he points out, ''76 percent of incumbent senators who had competitive races (the winner taking less than 60 percent of the vote) survived. In '76 and '78, it was 47 percent for competitive races. In '80 it was closer to 25 percent.''
The Democrats' objective this year should be ''slip the election,'' Hart says , that is, hold their share of Senate seats. ''Over the next two elections, the Republicans have 41 seats up, the Democrats 26 seats - 15 seats fewer,'' he says. ''In order for the Republicans to keep their majority they have to win two-thirds of the races. In '84 and '86 they're the vulnerable ones.''
Kansas Republican Sen. Robert Dole's warning that Reagan could be a ''lame duck'' president if his party lost control of the Senate this fall sounds unconvincing to congressional experts. They point out that since 1930, Republican presidents have had only two years - 1953 and 1954 - when they controlled a chamber in Congress. Eisenhower had six years, and Nixon six years of effective White House leadership without control of either House, they say. The larger immediate danger for Reagan would be the perception that the Republican resurgence had stalled so quickly, lessening his influence on Capitol Hill.
A state by state assessment by political professionals in both parties shows the Democrats firming up a few seats over the winter.
The seat of Sen. Henry M. Jackson (D) of Washington, considered a target by Republicans last fall, now looks out of reach to them, Republicans say. The Republicans still think they can soften up another Democratic power, Sen. Robert C. Byrd of West Virginia. But Mr. Byrd, forewarned, has hired political strategists to design a more sophisticated campaign, the Democrats counter.
Liberal Democratic Sen. Paul Sarbanes of Maryland is still rated a better than even shot by Republicans, but they feel their opportunity is slipping away. ''We're letting him off the hook,'' says one disappointed Republican strategist.
Republicans see their strongest takeover prospect in New Jersey's seat, held by Harrison A. Williams Jr., who faces Senate censure for a recent Abscam conviction. The Democrats think Republican Rep. Millicent Fenwick of New Jersey would be a formidable opponent, but are unconvinced she will win the nomination.
The Democrats think Tennessee's Sen. James Sasser's reelection drive is catching on. They look to the race as a bellwether for South and border state races in the future, as a test of a moderate Democrat's staying power where conservatives have been taking over.
A recent Republican surprise is the reported vulnerability of Sen. Robert T. Stafford (R) of Vermont. The Democrats still consider the state strong for the GOP, but Republican strategists worry a bitter primary fight would hurt the party.
Republicans are breathing more easily about Sen. Lowell Weicker's seat in Connecticut. The Democrats still think they can win with Rep. Toby Moffett (D) of Connecticut, if the Republicans squabble long enough. But Republican strategists say Senator Weicker, a maverick, is ingratiating himself again with the party's loyalists. ''Press Bush,'' Vice-President Bush's brother, ''has caught no one's fancy,'' one GOP pro comments.
In the West, the Democrats are fgllowing a small state strategy, the Republicans warn. That is, the Democrats hope to pick off some states where fewer dollars and other resources could have more impact than in the big states.
The Democrats as much as concede this. They see chances for upsets of Republican Sens. Harrison H. Schmitt of New Mexico, Orrin G. Hatch of Utah, and Malcolm Wallop in Wyoming. ''Remember,'' says a Democratic strategist helping to run his party's Senate campaigns, ''these Rocky Mountain states are not the rock-ribbed Republican states people take them to be. All three now have Democratic governors, and all recently had Democratic senators.''
SENATE RACE CHART Dem GOP Democratic incumbent seats rating rating East Maine Mitchell 0 -1 Md Sarbanes 1 0 Mass Kennedy 2 2 NJ Williams 0 -2 NY Moynihan 1 1 MIDWEST Mich Riegle 1 0 Neb Zorinsky 1 0 N D Burdick 1 0 Ohio Metzenbaum 1 0 Wis Proximre 2 2 WEST Ariz DeConci ni 1 0 Hawaii Matsunaga 2 1 Mont Melcher 1 1 Nev Cannon 1 1 Wash Jackson 2 2 SOUTH Florida Chiles 1 0 Miss Stennis 1 -1 Tenn Sasser 1 -1 Tex Behtsen 1 0 Virgina H.Byrd 0 -1 W. Va R.Byrd 1 -1 Republican incumbent seats EAST Conn Weicker 0 1 Del. Roth 1 2 PA Heinz 2 2 RI Chafee 1 1 VT Stafford 1 0 MIDWEST Ind L ugar 2 2 Minn Durenberger 1 1 MO Danforth 2 2 WEST Calif Hayakawa 0 0 NM Schmitt 1 1 Utah Hatch 0 1 Wyo Wallop 1 1 RATING: 2 strong for incumbent party 1 leaning 0 even -1 in doubt -2 likely loss