Six weeks after Ronald Reagan's sweeping reelection victory, some political experts see the President in a defensive posture on the issue of the nation's huge budget deficit. He has been throwing out some budget ideas but backing no bold initiatives and making no effort to build a bipartisan coalition to grapple with the problem.
Early assessments, based on his actions so far, are that the President will focus primarily on foreign policy in his second term. On the domestic front, analysts believe, he basically will pursue the course of the past three years.
''He's calling forth all the old budget cuts and holding back on the tax side ,'' says political scientist Thomas Mann.
''He has an opportunity to influence what government does, but he appears to have rejected the idea of a grand coalition that would put together a deficit-reduction package.''
''Except for the breakthrough with the Russians, he wants his second term to be a replay of the first,'' says Allen Schick, a budget expert at the University of Maryland. ''He seems to be conveying that on the domestic side he wants to continue what he did in the first term - cut a little deeper into government spending, go on with the military buildup, and have no tax increase. So there are no great departures.''
But, experts say, this may be only the President's opening round in the maneuvering with Congress. Reagan's customary political strategy, one followed when he was governor of California, is to hang tough on his own objectives, wait for the opposition to coalesce, and then begin pragmatically to bargain and accommodate himself to what the legislative and political traffic will bear.
Meanwhile, putting a US-Soviet arms control agreement at the top of his agenda, the President is actively preparing for the coming meeting between Secretary of State George P. Shultz and Soviet Foreign Minister Andrei A. Gromyko. According to White House officials, Reagan each week chairs a special ''President's group'' of Cabinet-level officials to decide and coordinate US positions for the Geneva get-together, beginning Jan. 7. He will have at least one such meeting this week, then conduct a final session in the first week of January.
''He is fully engaged and being given guidance,'' says a White House aide. Diplomatic experts attach significance to the President's heightened interest because he has not been closely involved in the past and his knowledge of the nuclear arms field is limited. Now there appears to be a concerted effort to prepare Reagan in a complex area in which he will face critical decisions.
Unlike the early weeks after the 1980 election, the President is claiming no big popular mandate for change or initiating moves to put the Congress on the defensive. His Treasury secretary, Donald Regan, has launched a bold tax-reform plan, but the President has not fully embraced it. His budget director, David Stockman, has proposed a slowdown in defense spending, but Reagan appears to be siding with Defense Secretary Caspar Weinberger, who opposes deep defense cuts.
''There are no signs of what he will do,'' says presidential scholar Stephen Wayne. ''He's throwing up trial balloons as if realizing that there is no majority for anything. He will see where the chips fall and take sides wherever he has potential support or can beat the opposition. So he's playing a poker game now, keeping the cards close to his chest.''
While his aides quarrel over policy, the President also faces contention from fellow Republicans in Congress. Senate Republicans are giving signals that they want the GOP to be seen not only as holding power, but also acting responsibly. They are therefore ready to oppose Reagan in some areas and nudge him in directions he would not normally take.
''Reagan's a lame duck, and it's being shown already,'' says Austin Ranney, a political expert at the American Enterprise Institute. ''Senate Republicans are looking to the '86 election and making sure they will minimize their losses. The selection of (Sen. Robert) Dole as majority leader is a clear signal.''
Pressures on the President from Republicans in Congress have begun. Sen. Richard Lugar of Indiana, new chairman of the Senate Foreign Relations Committee , and other conservatives persuaded Reagan recently to speak out strongly against apartheid in South Africa, something he has not previously done.
Also reflecting the tug and pull in the GOP, Sen. Barry Goldwater of Arizona, expected to be the new chairman of the Armed Services Committee, has come out against the MX missile, which the President wants as a bargaining chip in his negotiations with Moscow. Sen. David Durenburger of Minnesota opposes restoring US aid for the contra rebels in Nicaragua. And a number of Republicans are saying that a tax increase as well as a military slowdown will be necessary to close the budget gap.
Analysts see the President and his counselors increasingly concerned about a new economic recession. Hence, Secretary Regan's recent assault on the Federal Reserve Board, threatening to bring it under more direct White House control - a move some experts view as an effort to provide a scapegoat for the unrelenting budget deficit. Unknown is whether the President believes that sharply reducing the budget deficit would have a positive effect in warding off recession; during the campaign he conveyed that the deficit was not important.
''What we do know is that the package (of budget cuts and no tax increase) he has been talking about now will not fly,'' says Dr. Mann. ''It will work only if it's viewed as credible by both parties in Congress, and it can't be characterized as that now. He could be successful if he was willing to bite the bullet.''