Former Alabama governor George C. Wallace was forced into a runoff yesterday as he went before the voters for the first time in six years, seeking the Democratic nomination for an unprecedented fourth term.

Wallace will face the runner-up, Lt. Gov. George McMillan, a self-styled "New South Progressive," in a runoff Sept. 28.

Primary elections also were held in Arizona, Florida and Connecticut. Alabama

With 74 percent of precincts reporting, Wallace had 313,986 votes, or 41 percent; McMillan had 231,986 votes, or 30 percent, and house Speaker Joe McCorquodale 196,399 votes, or 27 percent. Former governor James E. (Big Jim) Folsom and retired attorney Reuben McKinley trailed.

Unopposed in the Republican primary was Montgomery Mayor Emory Folmar.

Appointed state supreme court Justice Oscar Adams held a slim lead in his bid to retain his job and become the first black elected to a statewide office in Alabama. Tom Haydsen of Birmingham was unopposed for Adams' seat in the GOP primary.

Wallace left the governor's mansion in 1978 after his second consecutive term, the maximum permitted. He had campaigned for the 1976 Democratic nomination for president in several state primaries before dropping out of the race. Florida

Democratic Gov. Robert Graham won more than 80 percent of the vote to defeat two rivals and win nomination for a second term, while Republicans chose five-term Rep. L.A. (Skip) Bafalis by a similar margin to oppose him Nov. 2.

Two-term Democratic Sen. Lawton Chiles was unopposed and, in the Republican Senate race, state Sen. Van Poole of Fort Lauderdale finished first but was forced into an Oct. 5 runoff with Palm Beach County State Attorney David Bludworth. Sarasota business consultant George Snyder finished third.

With 95 percent of precincts reporting, Poole had 142,035, or 42 percent; Bludworth 106,482, or 31 percent, and Snyder 90,778, or 27 percent.

In one of four new districts gained after the 1980 census, state Sen. Tom Lewis of North Palm Beach won the GOP nomination from Al Worden, an Apollo 15 astronaut. With 99 percent of precincts in, Lewis had 61 percent of the vote.

In the 19th District, Glenn Rinker, a former Miami TV anchorman, won the GOP race. With 94 percent of the precincts reporting, he had 83 percent of the vote to defeat contractor Herbert Hoodwin. The seat is held by Democratic Rep. Dante B. Fascell.

John L. (Gus) Plummer, a South Miami school bus driver and first black Republican elected to the legislature since Reconstruction, was defeated in his reelection bid by real estate agent Theresa Ashkar, who captured 60 percent of the vote. Arizona

State senate President Leo Corbet won the Republican gubernatorial nomination and the right to face Gov. Bruce Babbitt in November, while state Rep. Pete Dunn was nominated in the GOP Senate race.

Dunn will meet U.S. Sen. Dennis DeConcini, who won his nomination easily.

In the Republican Senate primary, with 330 of 1,350 precincts reporting, Dunn, of Phoenix, led with 19,884 votes, or 56 percent, to Mesa real-estate investor Dean Sellers' 15,396 votes, or 43 percent.

DeConcini quickly defeated Caroline Killeen of Tucson, a perennial candidate. With 341 precincts reporting, DeConcini had 34,649 votes, or 83 percent, to Killeen's 6,956 votes, or 16 percent.

With 273 precincts reporting, Corbet, of Phoenix, had 17,088, or 61 percent, to Glendale auto dealer Evan Mecham's 10,601 votes, or 38 percent.

In 1st Congressional District early returns, retired Navy officer John McCain led three opponents in the race to fill retiring GOP Rep. John J. Rhodes' seat.

With a new 5th District, a result of reapportionment following the 1980 census, state Sen. Jim Kolbe won the Republican primary and former state Sen. Jim McNulty gained the Democratic nomination. Connecticut

Democratic Gov. William A. O'Neill and Republican Sen. Lowell P. Weicker Jr. were unchallenged. Their November opponents were selected at party conventions. O'Neill took office when Ella Grasso, the former governor, died. He is seeking his first full term. Weicker will face Rep. Toby Moffett.

In the 6th District Democratic race, with all of the district's towns reporting, state Sen. William Curry, a former Moffett campaign aide, won with 14,211 votes, or 51 percent. State Rep. Gardner Wright had 6,895 votes, or 25 percent, and New Britain alderman Brendan Kennedy had 6,864, or 19 percent.

Republican state Sen. Nancy Johnson, endorsed by the party, won with 13,565 votes, or 70 percent, to real estate developer Nicholas Schaus' 5,780 votes, or 30 percent.