The 1982 campaign is winding up this weekend with prospects of continued conservative control of Congress and strengthened Democratic power in the state capitols.

Odds favor a standoff in the Republican-controlled Senate and a loss of fewer than 20 GOP House seats -- small enough to allow President Reagan to forge conservative coalition majorities of Republicans and southern Democrats, as he has for the past two years.

Democrats could come out of Tuesday's voting with two-thirds or more of the governorships, even though Republicans may control the statehouse in half of the 10 largest states.

That is the conclusion of The Washington Post's final preelection survey, based on campaign coverage by a dozen Post staffers, special correspondents in all 50 states and interviews with pollsters, campaign consultants and officials of both parties.

The state-by-state reports appear on Pages C4 and C5.

In estimating that the Republicans would lose fewer than 20 seats even if the Democrats captured all the doubtful districts, the survey is at odds with the national public opinion polls.

The final Gallup Poll last week said Democrats would receive 55 percent of the popular vote for the House, almost 4 points more than they did in 1980 and roughly equal to their 1978 share. That would indicate that they should regain the 33 seats they lost in the last election.

A Washington Post-ABC News poll of voters in 37 closely contested districts found the Democratic margin even larger, 59 to 41 percent, and said Democratic challengers were leading Republican incumbents in 12 of 19 GOP-held districts.

But a final, private preelection estimate at the White House, closely paralleling The Post's state-by-state survey, put the potential Republican losses in the 13-to-27-seat range, with 19 as the likeliest number.

Democrats do not disagree.

"I'm still at 15 seats," said Martin D. Franks, executive director of the Democratic Congressional Campaign Committee.

But the gap between the national polls and the district-by-district analyses makes everyone nervous.

"It's befuddling," said Nancy Sinnott, Franks' counterpart at the Republican Congressional Campaign Committee.

A week ago, Republicans were fearful that a trend was developing that might not only push their House losses above 30 seats but also yield the Democrats the five-seat gain that would end GOP control of the Senate.

Between Oct. 8, when the announcement came that unemployment had reached a post-Depression high of 10.1 percent, and Oct. 18, when the pollsters were able to measure public reaction to the president's Oct. 13 speech on the economy, Republican candidates sagged and Democrats surged.

Polls in all but a couple of the 13 Republican-held Senate seats dipped into the danger range for the incumbents. But in the last 10 days, most of those Republicans have steadied or recovered.

"I'm much more optimistic now," said Richard B. Wirthlin, the Reagan pollster monitoring many of those races. "I thought we were going to lose three or four [Senate] seats, but it's building back."

The Post survey found three incumbent senators in tossup races: Republicans John C. Danforth of Missouri and Harrison H. Schmitt of New Mexico, and Democrat Howard W. Cannon of Nevada.

A fourth tossup race is the Virginia contest between Rep. Paul S. Trible Jr. (R) and Lt. Gov. Richard J. Davis (D), to succeed retiring independent Sen. Harry F. Byrd Jr. Although Byrd voted regularly with Reagan and the Republicans, he caucused with the Democrats, so each party has two seats in maximum jeopardy.

But Republicans are in far greater danger of upsets in the Senate. Democrats have 15 safe seats on Tuesday; the Republicans, only Pennsylvania and Indiana. The Democrats have only three seats in the "leaning" category; the Republicans, nine.

Late trends in those nine states -- California, Connecticut, Delaware, Minnesota, New Jersey, Rhode Island, Utah, Vermont and Wyoming -- have generally favored the Republicans.

Sen. David F. Durenberger of Minnesota and Rep. Millicent Fenwick, the Senate nominee in New Jersey, both seemed in danger of being beaten by millionaire Democrats, but have recovered their leads in the last few days. In the spotlighted California contest, San Diego Mayor Pete Wilson (R) remains a few points in front of Gov. Edmund G. (Jerry) Brown Jr. (D).

None of these races can be called out of reach.

Patrick Caddell, the Democratic pollster who has been most bullish on his party's chances for a major midterm victory, conceded Friday that "an uptick in Reagan's support" seemed to be bolstering many Republican senators and senatorial candidates.

But, recalling his own experience with President Carter in 1980, Caddell said, "It's the last weekend when the party in power has to worry about things falling apart."

This weekend, Democrats are filling the air with pleas to voters to "send Reagan a message" protesting unemployment and warning against any tampering with Social Security benefits. But the better-financed Republicans are countering with televised and broadcast messages from Reagan himself, urging Americans to "vote your hopes and not your fears."

Discounting the likelihood of a late Democratic surge, Richard Bond, the deputy chairman of the Republican National Committee, said, "If there's an October surprise, it really will be a surprise."

While the battle for Congress -- the most expensive in history and, in many states and districts, the most personal and acerbic in recent memory -- centered on the national economy, Democrats appeared likely to make their greatest gains in the gubernatorial races where state issues dominate.

Democrats have a 27-23 edge in governorships now, with 36 statehouses on the ballot Tuesday. Of these, 20 are held by Democrats, 16 by Republicans.

Democrats have safe leads in 11 of the 36 and are clear favorites in eight more. Among those eight are five states -- Michigan, Minnesota, Nevada, Ohio and Wisconsin -- where Republicans are now in power. Republicans enjoy a comparable favorite's status in only six states, all with incumbents running.

If the 11 remaining battleground races split about evenly, Democrats could emerge in control of 33 states.

The last time the Democrats held more than 30 governorships was in 1974, and their grass-roots power helped them win the presidency in 1976.

Despite the prospective Democratic advantage, Republicans could have some bright spots in Tuesday's gubernatorial voting. In the last week, California Attorney General George Deukmejian (R) has surged into a position to upset Los Angeles Mayor Tom Bradley's bid to become the first black elected governor in American history.

In Alabama, Montgomery Mayor Emory Folmar (R) looms as a serious roadblock to former governor George C. Wallace's ambition to return to power. Even more surprising, businessman Richard H. Headlee is moving close to Rep. James J. Blanchard (D) in late polls for the Michigan governorship, an office Democrats felt sure they were going to reclaim after 20 years.

Incumbent Democrats are in tough fights for reelection in Idaho, Kansas and New Hampshire, and incumbent Republicans face serious challenges in Arkansas and Texas.

Weak economies and serious budget problems plague many of the incumbent governors, but in some of the hardest-hit states, Republicans such as Pennsylvania's Richard L. Thornburgh, Illinois' James R. Thompson and Oregon's Victor G. Atiyeh are rolling to reelection. In Atiyeh's state, where the wood products industry has been at Depression levels, Republicans are even throwing serious challenges at Democratic Reps. Les AuCoin and James Weaver.

By contrast, in Indiana, Ohio and Michigan, where the auto industry layoffs have been most severe, Democrats can count only four House districts in all where they have reasonable prospects of beating Republican incumbents.

This is partly because of the way the district lines were drawn; partly because of the Democrats' general shortage of cash for challengers, and partly because of the $50 million expenditure the Republicans have made over the last two years on House contests.

Most of that has gone into defending incumbents, and the seeming success of that effort is the main reason both parties' professionals discount the polls' predictions of a likely 30-plus seat Democratic gain.

A test case may occur in the Peoria district of House Minority Leader Robert H. Michel (R-Ill.).

The Democrats did not recruit a candidate until after the filing deadline for the primary, and had to run a write-in campaign to get lawyer G. Douglas Stephens on the ballot.

A month before the election, newcomer Stephens had spent only $75,000, just one-fourth of the veteran Michel's outlays.

But this weekend, bolstered by a late rush of contributions and vans of volunteers from Democratic headquarters in Washington, Stephens was suddenly more optimistic that high unemployment and low farm prices would end Michel's career.

Republicans, dismissing the opposition as too little and too late, said Michel "is ready to ice the champagne." Three or four other House veterans would like to join him, but in some cases, it might be a bit premature.

In Miami, Rep. Dante B. Fascell (D), third most senior member of the House Foreign Affairs Committee, has battled a stiff challenge by TV anchorman Glenn Rinker (R) but a late poll gives him a slight lead.

Similarly, Rep. Phillip Burton (D) of San Francisco, No. 2 on the House Interior Committee, gave up some good Democratic territory in his own controversial California redistricting plan, but reports indicate he may survive the challenge of state Sen. Milton Marks (R).

Less likely to be back is Rep. Don H. Clausen (R-Calif.), the second most senior minority member of Interior, who is fighting redistricting, lumber layoffs and a tough foe. But against all odds, another intended victim of the "Burton-mander," Rep. John H. Rousselot (R-Calif.) may prevail in a heavily Democratic and Hispanic district against freshman Rep. Matthew G. (Marty) Martinez (D-Calif.). That is one of six double-incumbent showdowns forced by redistricting.

In the most publicized of those battles, Rep. Barney Frank (D-Mass.) is favored over Rep. Margaret M. Heckler (R-Mass.). Democrats are favored in the matchups in Missouri and South Dakota, Republicans in New York.

As usual, the overwhelming number of House incumbents have used the visibility of their office and their fund-raising advantages to cement their prospects for reelection in any kind of political climate.

The Post survey counted 185 Democratic incumbents and 121 Republican incumbents as safe. Also, 26 open seats seem safe for one party or the other, 18 for the Democrats and eight for the Republicans.

Of the 10l competitive districts -- 77 now held by incumbents and 24 open -- 38 lean to the Democrats, 44 to the Republicans with 19 too close to call. If both parties hold the seats they are favored to win and the Democrats get all the tossups, their net gain in the House would be 19 seats, the figure the White House independently estimated.

These figures omit the two Atlanta-area Democratic districts where elections have been postponed to Nov. 30 by redistricting disputes.

A loss of fewer than 20 seats would be of normal dimensions, by historical standards, and would likely preserve Reagan's chances for constructing a majority conservative coalition on most tax and spending issues. His strongest supporters seem likely to be back in force. Of the 52 freshmen Republicans elected on his coattails in 1980 and seeking another term, 29 are safe, 16 are favored and only seven are in even or uphill races. Of the 35 "Boll-Weevil" southern Democrats who contributed their votes, 30 are safe, three are favored and only two are facing tough races.

But these district-by-district estimates could be awry, if there is a national trend. And the polls say the Democrats have the materials for a trend. Unemployment, a traditional Democratic issue, is the problem most voters rate uppermost and they judge the Democrats as the best party to handle it.

Many observers believe that blacks, who have consistently opposed Reagan and his programs, are ready to take their opposition to the polls in record numbers.

Polls by both parties confirm the view of Vincent Breglio, director of the Republican Senatorial Campaign Committee, that "if there's a low turnout, we Republicans are in big trouble. There is a segment of the Democratic Party that is following the race very closely, has rallied around the party label, and is full of high-probability voters."

But after 20 years of declining voter turnouts, the pattern may be ready to reverse. Republican pollster Robert Teeter is predicting a higher percentage turnout than in 1978 and the Gallup Poll said those expressing much or some interest in the election is higher than in 1978 or 1974.