With only hours to go before Americans begin voting, both Republicans and some independent analysts are predicting that an election sweep for President Reagan will bring with it a Congress friendlier to his programs.
Although the Republicans are still far from taking over the US House of Representatives, where the Democrats have a 99-seat edge, GOP candidates are pushing hard in at least 30 districts. If the party emerges with a gain of 18, that would probably be enough to return the House to the tenor of 1981, when President Reagan was able to command a working majority of House Republicans and conservative Democrats.
Moreover, even if some Democratic newcomers win in Southern districts, they would likely be of the type to join the so-called Boll Weevils, a group of House Democrats who often side with Mr. Reagan.
Meanwhile, Democrats, who had some lingering hopes of big gains in the Senate , have scaled back their expectations to picking up two seats in the GOP-controlled upper chamber.
However, the focus of the last week of the national campaign has been on the House, the last stronghold of the Democrats. The Republican Party turned on its well-financed machinery to crank out mailings and television ads reminding Americans of Democratic nominee Walter F. Mondale's promise to raise taxes and urging them to send GOP candidates to Congress.
Vice-President George Bush and President Reagan, now confident of holding the White House, have taken their entourages into marginal congressional districts to stand next to GOP candidates and urge voters to endorse the whole GOP ''team.'' Although delayed until the last minute, the all-out drive came just as voters were making their decisions on congressional races. It also came just as a Gallup poll found 46 percent of voters leaning toward Republicans for Congress , up by four points over 1980, when the GOP gained 34 seats.
This year the Republicans are pursuing some prizes long denied them, like the suburban Pennsylvania district of Rep. Robert W. (Bob) Edgar. One of most Republican areas in the country, the Seventh District has persisted in choosing the liberal, Democratic Edgar ever since the Watergate scandal helped elect him in 1974.
But a 3-to-1 Republican registration advantage has always meant hard election battles for Representative Edgar. This year he is also battling Reagan popularity in his district. A week ago, the President swooped in for a courthouse rally in Media, Pa., for Republican candidate Curt Weldon.
One Pennsylvania GOP official has been quoted as saying, ''We've thrown everything into this race but the kitchen sink.''
The Edgar camp has felt the pressure, and the incumbent has spent a half-million dollars on the race. However, the congressman - a Methodist minister who wins on his squeaky-clean image - held that he felt no aftereffects from the presidential visit. He is nonetheless waging a relentless campaign.
On a chilly evening during the last weekend before the elections, Edgar spent two hours standing outside grocery stores, greeting shoppers, most of whom were Reagan supporters.
''Don't tell anybody,'' said a middle-aged man as he shook his congressman's hand. ''I'm a Republican. I'm going to vote for you.''
One couple recounted help the congressman had given them with the Veterans Administration and confided that they had changed their party registration just for Edgar.
But inside the store, Upper Darby homemaker Barbara Frey, a loyal Democrat in the past, said she plans to vote a straight Republican ticket this year. The reason is not displeasure with her congressman so much as her general view about her life today.
''I think I'm a lot better off,'' she said. ''I was able to quit work, have another child, and buy a house. We got a good mortgage rate. It's a lot different than it was.''
Republicans face two hurdles in trying to take a district like Edgar's. First he has been in office long enough to establish himself with his constituents. Second, some voters like the idea of having a Democratic Congress as a check on President Reagan.
That includes voters like Paul Sabatini, a retiree from Marple Township in Edgar's district. ''I don't like Mondale, period,'' he said as he wheeled a grocery cart. ''I'm going to vote for Ronald Reagan - and Edgar.''
Why a Democrat for Congress? ''I like to have the House Democratic so Ronald Reagan can do no harm,'' said Mr. Sabatini.
Republicans have long spotted that sentiment in their polling. And so in the campaign they are turning to calling for the ''Reagan team'' or the ''Republican team,'' as they urge voters to vote straight GOP tickets. Rep. Guy Vanderjagt of Michigan, chairman of the National Republican Congressional Campaign Committee, said in a TV ad aired Saturday that voters should reject the ''liberal team'' of Democratic House Speaker Thomas P. O'Neill Jr.
Vice-President Bush, speaking to an overflow crowd in Towson, Md., made Mr. O'Neill his chief target. ''We've got to pick him up and move him over,'' he said as he endorsed GOP candidate Helen Bentley in her third and tightest campaign against veteran Rep. Clarence D. Long. The Bush line is one he has used to draw cheers from crowds across the country.
The Republican congressional committee has increased its prediction to a gain of 25 or more House GOP seats. The Democratic campaign committee disputes that. ''Our people are not panicking,'' said a Democratic spokesman. ''They aren't calling us. They've been dealing with prospects of a Reagan landslide for two months.''
But independent observers saw signs of substantial GOP gains as the campaign pulled to a close. ''My instincts still say'' the gains will be in the ''low teens,'' said Bernadette Bude, an official with Business-Industry Political Action Committee since 1972. ''But instincts have to be placed on hold if there is a sweep.''
She predicted that a GOP sweep will protect all Republican seats, while toppling 18 or 19 Democrats.
Charles Cook, editor of a political newsletter and a former Democratic congressional staffer, said, ''I think it's certainly over 20, and I think it's over 25 seats.'' He said he saw evidences of a snowball effect, such as happened in favor of the Democrats two years ago and for the GOP in 1980.
But he added that the Republican pull is not simply a matter of riding the coattails of a popular president, but the improved economy, general optimism, worry about Democrats raising taxes, and disaffection of men and whites from the Democratic Party.