Bolstered by startling conservative victories in Indiana, Idaho, South Dakota and Iowa, the Republicans early this morning were close to grabbing control of the Senate but failed to upset the Democratic majority in the House of Representatives.

Key liberal Democratic leaders, including Sen. Birch Bayh (D-Ind.), Sen. Frank Church (D-Idaho) and Sen. Warren G. Magnuson (D-Wash.)--who head the Senate Intelligence, Foreign Relations and Appropriations committees, respectively--all fell to GOP challengers.

Liberal Sens. George S. McGovern (D-S.D.) and John C. Culver '54 (D-Iowa) also lost to conservative challengers, who were backed by New Right and evangelical political action committees.

Overall, the Republicans picked up at least seven new Senate seats. In New York, Rep. Elizabeth Holtzman (D-N.Y.) narrowly lost to conservative Alfonse M. D'Amato, but Holtzman called for a recount early this morning.

The Democrats dropped more than 30 spots in the House but retained a sizable, majority.

On the House side, Majority Whip John Brademas (D-Ind.) and Rep. Al Ullman (D-Wash.), chairman of the House Ways and Means Committee, energy specialist Rep Robert Echhardt (D-Tex.), and urban expert Rep. Thomas Ashley (D-Ohio) all lost to Republican opponents.

Both House Speaker Tip O'Neill (D-Mass.) and House Majority leader Jim Wright (D-Tex.) easily weathered the Republican hurricane. In a tough, uphill battle liberal spiritual leader Rep. Morris K. Udall (D-Ariz.), chairman of the House Interior Committee, surprised the grave-watchers and won by an almost two-to-one margin.

McGovern last night attributed the wave of Republican Senate victories to "a new virulence of the new extremism." In a post-election interview, the former presidential candidate and influential member of the Senate Foreign Relations Committee condemned the "scurrilous literature" used by conservative lobby groups and said the increasing role of single-issue political action committees has "poisoned the political climate."

Refusing to criticize the tactics of conservative Republicans, Bayh last night credited Reagan's overwhelming triumph for sweeping so many Republicans into Congress.

More moderate Democrats managed to hold off the aggressive Republican assault especially in the Midwest. Alan J. Dixon, for example, defeated David O'Neal for the seat of Sen. Adlai Stevenson (D-Ill.), while incumbent Sens. Thomas Eagleton (D-Mo.) and John Glenn (D-Oh.) overcame Republican challengers. Sen. Gary Hart (D-Colo.) pulled out a last-minute victory over Mary Estill Buchanan.

Despite these victories and the continuing Democratic leadership of the House, Republicans confidently anticipate increased power in a more conservative Congress. Although the shift to the right should aid the Reagan administration in its efforts to cut taxes and raise defense spending, the loss of so many experienced leaders will probably hurt Congress' often-questioned efficiency.

In other important contests, Sen. Herman Talmadge (D-Ga.), head of the Senate Agriculture Committee, overcame accusations of corruption and an official Senate "denouncement" to defeat opponent Mack Mattingly, while incumbent Sens. Alan Cranston (D-Calif.), Ernest Hollings (D-S.C.), Robert Dole (R-Ka,) and Paul Laxalt (R-Nev.) all marched to convincing victories.

Unlike Talmadge, several House members were crushed by scandal. Indicated Abscam conspirators Reps. John Jenrette (D-S.C.), Frank Thompson (D-N.J.), John Murphy (D-N.Y.), and Michael Myers (D-Pa.) all lost, as did Rep. Robert Bauman (R-Md.), who had to answer to charges of alcoholism and homosexuality.

The much-publicized effort to put more women on Capitol Hill seemed to have fallen short. On the Senate side, Paula Hawkins, a Republican conservative from Florida, defeated former Congressman Bill Gunter in Florida, but Buchanan, Mary Louise Faust (Kentucky) and Mary Gojack (Nevada) all lost their Senate bids.

In other regional races, Rep. Christopher J. Dodd. (D-Conn.) defeated James L. Buckley in the Connecticut race for retiring Sen. Abraham D. Ribicoff's seat. In New Hampshire, incumbent Sen. John Durkin (D-N.H.) narrowly lost to conservative challenger Warren Rudman. The Vermont contest between Sen. Patrick Leahy (D-Vt.) and Steward Ledbetter was too close to call.

With 13 governorships up for grabs, the Republicans and Democrats each won six, with the race in North Dakota still uncertain at 3:30 a.m. The biggest upsets were scored in Arkansas, where Republican Frank White defeated incumbent Bill Clinton and in Missouri, where Republican Christopher Bond defeated Joseph P. Teasdale.

In neighboring Rhode Island, incumbent Gov. Joseph Garrahy easily defeated the popular mayor of Providence, Vincent "Buddy" Cianci