Once the fortress of the Democratic Party, the eastern section of the country opened the gate for Ronald Reagan, with Republicans adding such key Democratic states as Massachusetts, Maryland, New York and West Virginia to their sweeping coast-to-coast victory.

Though the East was the only area of the country where it seemed possible for Democratic presidential nominee Walter F. Mondale to give Reagan at least some competition, even Massachusetts, the only state that voted for Democrat George McGovern in 1972, turned against Mondale. After tantalizingly giving Mondale a lead early in the evening, final tallies showed that even with its liberal reputation the Bay State stood in line with the rest of the country to back Reagan.

West Virginia, which was President Jimmy Carter's best state behind Georgia in 1980, went soundly for Reagan this year as the president's message appeared to be getting through even to people who were among those suffering the worst from the recession two years ago.

Even Rhode Island, which had gone Republican for president only three times in the last 55 years, decided this year to make it a fourth, as bitter in-fighting among the Democrats eroded what little hope Mondale had.

Maryland, which had lined up with the Democrat in five of the last six presidential elections, made the turn this time to Reagan. And New York state joined Pennsylvania as the big eastern industrial state that went to Reagan two presidential elections running.

Only the District of Columbia as usual went strongly Democratic.

Vermont provided one of the few possible surprises of the evening as Democrat Madeleine M. Kunin was bucking the Republican tide in her effort to become the first woman governor of this increasingly independent state.

New Hampshire, the state that launched the presidential primary season by this year giving Mondale his first upset to Sen. Gary Hart (D-Colo.), went easily to Reagan. And New Jersey, which has not voted Democratic since the Lyndon B. Johnson landslide in 1964, also stood by the president this year.

GOP strategy in much of the Northeast was to concentrate on the suburbs, where Republicans not only wanted to win votes Tuesday but also to convince voters it was time to make the big leap from the party of Roosevelt and Kennedy to the new Republicanism of Ronald Reagan. Connecticut, a stretch of suburbia surrounding a few urban Democratic centers, fell easily into Reagan's pocket as did Vermont, Maine and Delaware.

But more than a realignment of the parties, the GOP also was hoping to shift the political tenor of Congress. However, their hopes to pick up an additional senator from West Virginia were dashed when Gov. John D. (Jay) Rockefeller IV held onto the seat left open by retiring Sen. Jennings Randolph (D). Connecticut

Reagan easily carried Connecticut, which has voted Republican in every election since 1972.

With no races for governor or the Senate, the closest contest was between freshman Rep. Bruce A. Morrison (D) and former representative Lawrence J. DeNardis (R). Morrison appeared to have held on to his seat, carrying the district by a narrow margin.

Morrison beat DeNardis two years ago by fewer than 2,000 votes. DeNardis based much of his campaign on Reaganomics and had been expected to benefit from a strong Reagan showing in the state.

In another closely fought House race, Rep. William R. Ratchford (D), who was seeking his fourth term, was narrowly defeated by state Rep. John G. Rowland (R) from Waterbury, the largest city in the district. Both Reagan and Bush visited the district to campaign for Rowland, and Ferraro appeared there on Sunday to campaign for Ratchford.

In Connecticut's remaining four congressional races, two were expected to be carried easily by incumbent Democrats, one by an incumbent Republican. In the fourth, Rep. Nancy L. Johnson (R) was winning by a large margin over insurance executive Arthur H. House (D). Delaware

Reagan easily captured Delaware, a state largely ignored by the national candidates, and the GOP retained control of the statehouse. Lt. Gov. Michael N. Castle (R) easily defeated rival William T. Quillen (D) in a bid to succeed retiring Gov. Pierre S. (Pete) du Pont IV.

But neither Reagan's coattails nor her husband's popularity were sufficent to pull Elise R. W. du Pont (R) to victory over freshman Rep. Thomas R. Carper (D) in the state's single congressional district.

Carper, a tough campaigner who bucked a Republican tide to wrest the seat from a three-term incumbent in 1982, sustained a wide lead over du Pont, who had abandoned a sedate campaign of "home visits" in favor of heavy-hitting television attacks against her opponent.

Despite the state's decidedly Republican mood, Delaware voters reelected Sen. Joseph R. Biden Jr. (D) by a wide margin over Milford businessman John M. Burris (R). Maine

Reagan won in Maine, a state the Mondale campaign had high hopes of carrying despite the fact that it went Republican in the two previous elections.

Sen. William S. Cohen (R) easily defeated state House Majority Leader Elizabeth H. Mitchell (D) to win a second term.

Rep. Olympia J. Snowe (R) defeated two opponents to win a second term.

The race in Maine's southern congressional district was closer, but freshman Rep. John R. (Jock) McKernan Jr. (R) appeared to have fought off a strong challenge from former Democratic state chairman Barry H. Hobbins to win a second term. Maryland

Reagan became the second Republican to win Maryland in the last 28 years, despite last-minute efforts by both Mondale and Ferraro to keep one of the most stalwart of Democratic states in their column.

Even though Reagan had led consistently in the polls since September, Democratic officials had hoped that a big turnout of black voters in Baltimore and Prince George's County could turn the tide.

Meanwhile, Republicans gained a second seat in Maryland's eight-member congressional delegation. Former Federal Maritime Commission chairman Helen Delich Bentley (R) was successful in her third attempt to unseat 11-term Rep. Clarence D. Long (D). Other incumbents, six Democrats and a Republican, cruised to reelection. Massachusetts

Reagan very narrowly defeated Mondale to carry Massachusetts. Since 1960, the state had chosen a Republican presidential candidate only once, and that was Ronald Reagan in 1980.

Lt. Gov. John F. Kerry (D), who is best known for his role in the early 1970s as the leader of Vietnam Veterans Against the War, defeated conservative businessman Raymond Shamie (R) by a wide margin in the contest for the seat of retiring Sen. Paul Tsongas (D).

Democrats had worried that Shamie, who ran unsuccessfully in 1982 against Sen. Edward M. Kennedy (D), might build momentum after his upset primary vistory over former U.S. attorney general Elliot L. Richardson (R), but disclosures of Shamie's past ties with the John Birch Society hurt his chances.

In the most highly publicized House contest in Massachusetts, Rep. Gerry E. Studds (D), who was censured by the House in 1983 for a homosexual affair a number of years ago with a congressional page, used a strong organization and record of constituent service to defeat Lewis Crampton (R), a former official of the U.S. Environmental Protection Agency. Studds was seeking his seventh term.

In one of the closer races in the state, Chester G. Atkins (D), head of the Ways and Means Committee in the state Senate, defeated attorney Gregory S. Hyatt (R), who ran an antitax campaign. The two were competing for the seat vacated by Rep. James M. Shannon (D), who ran unsuccessfully for the Democratic Senate nomination.

Among the remaining congressional districts, all were expected to be won easily by the incumbents, eight Democrats and one Republican. New Hampshire

Reagan won a major victory in this traditionally conservative state, which has gone for a Democrat only once in the past six presidential elections.

Gov. John H. Sununu (R) won a second term by a wide margin over state House Minority Leader Chris Spirou (D).

In the Senate race, incumbent Gordon J. Humphrey (R) defeated Rep. Norman E. D'Amours (D). Humphrey, who was elected in 1978 as a militant conservative, worked this year to put himself in New Hampshire's political center, appealing to conservative Democrats, while D'Amours courted moderate Republicans and independents. A heavy crossover vote was expected.

State Republicans were determined to take over the congressional seat D'Amours vacated, and third-time candidate Robert C. Smith (R), a real estate agent, was holding a wide lead over state executive counselor Dudley Dudley (D), a liberal activist whose role in past presidential primaries has made her one of the better-known female politicians in the country.

In the remaining congressional race, Rep. Judd Gregg (R) defeated his two challengers. New Jersey

In the Garden State, which last went Democratic at the presidential level in 1968, even Reagan's tide could not sweep Sen. Bill Bradley (D) out of office. Indeed, Bradley was provoking his own surge, not only defeating Mary Mochary (R), mayor of Montclair, in the Senate race but also to taking a personal stake in efforts to keep eight of 14 House seats Democratic.

The one House seat considered a likely gain for the Republicans was in the northern Newark suburbs where Rep. Joseph G. Minish (D) was recently mapped out of his district. Assembly Minority Leader Dean A. Gallo of Parsippany moved quickly into the most fertile new field for Republicans, the middle-class suburbs, to win the district with a wide lead.

Gallo, a realtor, painted Minish as an anti-business liberal spender and criticized him for not hewing the Reagan line on the three-year tax cut, balanced budget and other Reagan efforts in Congress. New York

The biggest electoral plum in the East stayed with Reagan again this year, meaning that the Empire State has gone with the winner in presidential politics in every election since since 1960 except 1968 when New Yorkers went for Democratic nominee Hubert H. Humphrey.

With no Senate seat or governorship at stake, New Yorkers were electing 34 members of Congress. At least five House seats were being closely watched for possible party changes: two Republican and three Democratic.

Long Island freshman Rep. Robert J. Mrazek (D), had a slight lead over a man with money and presidential connections, Robert P. Quinn (R). The district has had a topsy-turvy political history in recent years with John LeBoutillier (R) winning on Reagan coattails in 1980, only to lose in the Democratic comeback in 1982.

Another key contest was in Manhattan's "Silk Stocking" district, where the cost running for the House seat was expected to top $2 million after Rep. Bill Green (R), who had a wide lead in later returns, and borough President Andrew J. Stein (D) crossed the finish line.

In western New York, veteran Rep. Stan Lundine (D) was ahead in his uphill battle with Jill Houghton Emery (R), a former teacher who enjoyed helping her husband run for state offices and decided to try it herself.

Ferraro's seat was expected to pass on to a fellow Democrat, Thomas J. Manton, and Fred J. Eckert (R) was expected to inherit the seat of one of the House stars, retiring Rep. Barber B. Conable Jr. (R).

For coattails watchers, retiring Rep. Richard L. Ottinger (D) left behind a bitter race between former aide Oren J. Teicher (D) and Scarsdale accountant Joseph D. DioGuardi (R). DioGuardi angered local blacks in September by remarking that minorities "enjoy having children" at least in part because "it gets them another check."

DioGuardi, who had a slim early lead, said that a vote for him would be a vote for Reagan in the Democratic House. Pennsylvania

A series of last-minute television commercials to bolster what they saw was a diminishing lead appeared to pay off for Reagan, who moved into the lead in early returns. Once a charm on the Democratic chain, Pennsylvania went easily for Reagan in 1980 and now has two Republican senators.

At least two House races were proving to be contested closely. Rep. Bob Edgar (D), who has held on to his seat in the Philadelphia suburbs by his fingernails each two years, was running 481 votes ahead of Delaware County Councilman Curt Weldon (R), who made much of Edgar's thinly disguised plan to run for the Senate in two years. The race is expected to be decided by write-in ballots.

Another crucial race in the Keystone State was for the seat of Rep. Peter H. Kostmayer (D). Kostmayer, who lost his job in Reagan's first sweep in 1980 but regained it in 1982, had a strong lead over Republican David A. Christian, a neophyte campaigner who was known as an activist on veteran's issues. Kostmayer's seat was expected to be one of the first to slip in a Reagan landslide. Rhode Island

The GOP claimed the statehouse and Reagan claimed the state, which was one of Carter's six states in 1980 and has not had a Republican governor since 1968.

In the governor's race, Cranston Mayor Edward DiPrete (R) edged out state Treasurer Anthony J. Solomon (D) in the race to succeed retiring Gov. J. Joseph Garrahy (D).

But Sen. Claiborne Pell (D) swept to a fifth term over business executive Barbara Leonard (R), and both House races appeared to be safely in the hands of the incumbents.

In the state's 1st Congressional District, Rep. Fernand J. St Germain (D) was rolling up a substantial lead in his bid for a 13th term over newcomer Alfred Rego Jr. (R), and Rep. Claudine Schneider (R) was defeating Richard Sinapi handily (D) for a third term from the 2nd district. Vermont

As expected, Reagan easily carried Vermont, which has supported Republican candidates in every presidential election since 1968.

The race for governor between Madeleine M. Kunin (D), the lieutenant governor, and state Attorney General John J. Easton (R), was too close to call, with an early lead by Kunin narrowing as votes were counted. Kunin, who was seeking to become Vermont's first female governor and the third Democrat ever to hold the office in 30 years, and Easton were competing for the seat vacated by retiring Gov. Richard A. Snelling (R).

Kunin, who was making her second try for the job after winning 44 percent of the vote in 1982, would become the nation's second female governor. Easton ran on law-and-order issues and stressed his role in acid rain control and consumer protection.

The state constitution requires the winner to receive 50 percent of the vote. With three minor candidates on the ballot, the decision could be left to the state House of Representatives, where Republicans expected to stay in control.

In the only other statewide election, Rep. James M. Jeffords (R) held a considerable lead over his three challengers and was expected to win a sixth term in the House. West Virginia

Reagan took West Virginia despite the state's high unemployment rates and strong Democratic tradition. It was only the second time since 1956 that the state had been in the GOP column for a presidential election, and Democrats faced unexpectedly tough sledding in statewide races.

Gov. John D. (Jay) Rockefeller IV (D) defeated wealthy businessman John R. Raese (R) for the seat of retiring Sen. Jennings Randolph (D), but only after waging an expensive campaign against a political newcomer who spent less than a tenth of Rockefeller's $7.8 million and whose campaign was plagued by gaffes.

Ex-governor Arch A. Moore Jr. (R) reclaimed his old job, defeating state House Speaker Clyde M. See Jr. (D) in a tight battle that see-sawed long into the night.

Republicans had hoped to snag at least one of West Virginia's congressional seats, all held by Democrats, but two freshmen who were believed vulnerable fended off tough GOP challenges.

Rep. Alan B. Mollohan (D) defeated Wheeling funeral director and civic leader James Altemeyer (R), and Rep. Harley O. Staggers Jr. (D) edged out former representative Cleve Benedict (R), who was trying to retrieve his old seat.