Why GOP could stray from President by '84

President Reagan finds himself in a struggle for control of his own party.

There will be no open break, Republican sources say. But Republican leaders will let President Reagan increasingly go his own way - anticipating he will hold to his basic 1980 agenda, they say. Meanwhile, Republicans in Congress will independently seek coalitions with Democrats on issues like jobs and social security reform, the items most likely to govern voter decisions in 1984.

This was the gist of the bad news GOP Senate majority leader Howard H. Baker Jr. and House minority leader Robert H. Michel gave President Reagan last week: that a move-up of next July's tax cut to Jan. 1 wouldn't pass muster, and the Senate leadership would work with House Speaker Thomas P. O'Neill Jr. on a major jobs bill instead.

Several forces are leading Republicans to go their own way:

* As things stand now, Republicans look likely to lose control of the Senate in 1984. Republicans have more seats at stake than Democrats. A Monitor survey of the strength of Senate incumbents for 1984 shows just two Democrats in potential trouble, compared with a dozen Republicans. Republican pros say a loss of three seats is the most optimistic outlook, with a loss of six the most likely outcome. A five-seat GOP loss would give Democrats control of the Senate. The Democrats already control the House.

* GOP incumbents are being encouraged by political strategists to look to their own resources for reelection, and to ''do their own thing'' as officeholders. The economic picture will at best be mixed, party strategists say. President Reagan's reelection intentions are iffy. He won't make a decision until next summer or fall, party officials say. Putting Sen. Paul Laxalt, a staunch Reagan ally, into the chairmanship of the Republican National Committee's (RNC) is a holding action, not a clear signal Reagan will run again, they say.

* The party mechanism itself - which waged an impressive assault in 1980 on House, Senate, and White House fronts - is not getting the attention it needs for 1984. ''Reagan is not a party builder,'' one GOP official says. Senator Laxalt is not the kind of take-charge force the party needs at the RNC, and White House chief of staff James Baker does not have the authority to manage GOP resources from the chief executive's compound, Republican officials say.

* Reagan may not face squarely enough the jobs and social security issues, party officials say. During this year's election, much was made of the fact that many Democratic voters who went for Reagan in 1980 indicated they were returning to their party.

But just as crucial, GOP pros say, was the defection of Republican voters in two key groups. The first was family-age adults, 35 to 54 years old, with some college or vocational training but no college degree. In 1980 they voted 58 percent for Reagan. This time they voted 55 percent for Democratic candidates for the Senate. They held jobs but said they feared for their jobs in the future. Similarly, 54 percent of pre-retirement adults ages 55 to 64 voted for Reagan in 1980 but nearly 60 percent went for Democratic Senate candidates in 1982. Their worry: the future of social security.

''If the White House shows a lack of leadership on these issues, the Senate Republicans will try to show which direction the country should go,'' a Republican administration official observes. ''So far, the White House dialogue has been reactive. There is no long-term thinking about changing directions or new directions.''

The highest-ranking Republicans inside and outside the White House are sharply split on whether Reagan will run again.

''Reagan has a four-year agenda,'' says one GOP official who worked for his election. ''I've never thought he was more than a one-term president. He still has the full-speed-ahead . . . mentality he took to the White House. I don't think he will run again, but we might not know until next July or August. If Reagan views the Republicans who are positioning themselves . . . as unacceptable, then that's a different ball game.''

Meanwhile, the positioning for 1984 is in full swing, encouraged by Reagan's posture. ''Reagan's behaving like a man whose agenda was set when he entered office,'' says a Republican professional. ''He won't succumb to pressures in this town or around the country. It makes for good drama, but it doesn't always make for good politics.''

Democratic and Republican professionals have been assessing the reelection strengths and weaknesses of Senate incumbents for 1984 since early this year. The close call in the November election for several Republicans has added a note of urgency to the Republicans' outlook. But the pattern of GOP vulnerability for 1984 has been apparent for some time.

The most vulnerable Republican seats appear to be those held by Sens. Jesse Helms of North Carolina, Roger Jepsen of Iowa, and Gordon Humphrey of New Hampshire. Mr. Helms, the New Right leader, will be challenged by North Carolina's Democratic governor, James B. Hunt Jr., who will enjoy broad national fund-raising support in his attempt to unseat Helms. Mr. Jepsen, regarded by many observers as a rather eccentric Senate performer, faces possible challenges from former Sen. Dick Clark (D) and Rep. Tom Harkin (D). Mr. Humphrey is seen by Republicans as too conservative for his state, but saveable.

Among other vulnerable GOP Senate seats is the one held by South Carolina's Strom Thurmond, who may not run again. Texas' John Tower is seen by many voters are preoccupied with national issues - to the neglect of Texans' concerns. Oregon's Mark Hatfield might retire. Illinois's Charles Percy seems headed into a bitter Republican primary race, opposed by Rep. Tom Corcoran, former Gov. Richard Ogilvie, or one of the two Crane brothers, Daniel and Philip, now in the House of Representatives. Minnesota's Rudy Boschwitz is viewed by some as too abrasive and could be a good Democratic target.

Among Senate Democrats, officials of both parties see Kentucky's Walter D. Huddleston headed for a strong GOP challenge, and Republicans add Delaware's Joseph R. Biden Jr. to the category. Otherwise, Senate Democrats up for reelection in 1984 appear in good shape. And potential Democratic challengers are poring over the long Republican vulnerability list, looking for opportunities.

Party pros look ahead to '84 Senate races Democratic incumbent seats Dem. GOP rating rating SOUTH Boren, David L. Okla. 1 1 Heflin, Howell Ala. 1.5 1.5 Huddleston, Walter Ky. 0 0 Johnson, J. Bennett La. 1 1 Nunn, Sam Ga. 1.5 2 Pryor, David Ark. 1 1 Randolf, Jennings W.Va. 1.5 1 West Baucus, Max Mont. 1.5 1 Midwest Exon, J. James Neb. 1.5 1 Levin, Carl Mich. 1 1 EAST Biden, Joseph R. Jr. Del. 1.5 0 Bradley, Bill N.J. 2 2 Pel, Claiborne R.I. 1 1 Tsongas, Paul E. Mass. 1.5 2 Republican incumbent seats SOUTH Baker, Howard H. Tenn. 2 1 Cochran, Thad Miss. 0 1 Helms, Jesse N.C. -1 -1 Thurmond, Strom S.C. 1 0 Tower, John Texas 0 0 Warner, John W. Va. 0.5 1 WEST Armstrong, Wm L. Colo. 1 0.5 Dominici, Pete V. N.M. 1.5 2 Hatfield, Mark O. Ore. 0 0 Simpson, Alan K. Wyo. 2 2 Stevens, Ted Alaska 0 2 MIDWEST Boschwitz, Rudy Minn. 0.5 0 Jepsen, Roger W. Iowa -1 -1 Kassenbaum, Nancy L. Kan. 1 2 McClure, James A. Idaho 1 2 Percy, Charles Ill. 0 0 Pressler, Larry S.D. -1 0 EAST Cohen, William S. Maine 1 2 Humphrey, Gordon N.H. -1 0 Ratings: 2 -- strong for designated party, 1 -- edge for incumbent party, 0 -- even, -1 -- likely loss of seat.