Washington — Election defeats have thrown the White House into what one insider calls a ''thoughtful pause.''
Top administration political hands, including Chief of Staff James Baker III, concede the plan to ''stay the course'' has hit a slight snag.
President Reagan and his aides must now assess the extent of the damage and then plot a strategy for keeping the administration's momentum going.
Administration strategists say they are moving into a testing period: They will have to find out whether the GOP House losses leave them with a working coalition there. The perception among White House aides is that some of the new Democrats will support moves to cut the size of the federal government, and will be inclined to vote for some of the President's spending cuts.
The chairman of the National Republican Congressional Committee, US Rep. Guy Vander Jagt of Michigan, says that in his early, quick study of the incoming Democrats he sees hope for this kind of cooperation.
''I see that some of those Democrats who were knee-jerk voters against Reagan programs have been defeated,'' he says. ''And I know that there are several among the new Democrats who are likely to listen carefully to what Reagan is proposing.''
The White House concedes that the President must now work even harder to get his programs through Congress. Representative Vander Jagt, talking to reporters over breakfast Nov. 3, said, ''No doubt about it, the President will have to have more consultations with the House as the result of this election.'' But Mr. Baker says the election results certainly don't turn the legislative initiative over ''to those who would like to spend and spend and tax and tax.''
But with the Republicans holding onto their majority in the Senate - apparently without losing a seat - and with fewer than 30 GOP House seats lost, the Reagan team says guardedly that it will be able to mush on somehow.
The Democrats charge that this is whistling in the dark. They say the new Democratic-controlled House will be so stacked against the President that his legislative effectiveness may well be neutralized for the next two years.
Indeed, some within the administration are privately expressing concern that changes in House makeup could bring about a stalemate in government. The President seems to be working to avoid that, however.
''We've had trouble the last 22 months,'' he said Wednesday. ''It's been a struggle every foot of the way. There have been concessions and compromises in both directions on all of the major issues, and we expect to continue to work with the Congress in that way.''
The President is understood to be taking heart in exit polls that, according to his aides, show strong support for him, his performance in office, and his economic program.
He also could take heart from Wall Street's reaction to the elections. The market staged a major rally Wednesday. Wall Street, according to analysts, apparently concluded that Reagan's economic program won't be quashed by the new Congress.
What becomes increasingly clear is that the President isn't likely to take his social programs - the prayer-in-school amendment, tax credits for tuition at private and parochial schools,and anti-abortion legislation - very far in the House when its new composition makes defeat seem likely for such initiatives.
There are those in the White House who will breathe a sigh of relief if they no longer have to spearhead such programs. They say these initiatives have little chance of passing and tend to dilute what they say should be the administration's top priority - economic matters.
The President is understood to be concerned by Democratic gains in governorships and state legislatures. He faces a Democratic political bastion now in almost all of the big, industrial states - which will give any Democratic presidential candidate in 1984 a particularly strong political base.
But out of the election came no highly visible, new Democratic stars. Gov. Edmund G. Brown Jr. (D) of California, a longtime luminary, faded out when he was defeated by San Diego Mayor Pete Wilson in California's US Senate race.
Observers here say that, based on Mr. Reagan's record of dealing with a resistant Democratic legislature during his second term as California governor, he may prove quite adaptable in dealing with a more heavily Democratic House.
At that time, Reagan continued to take a firm, apparently inflexible stands only to move to conciliation when he had to do so. Already, observers point out, Reagan has showed this ability to be conciliatory in his acceptance of the recent tax increase.